diff --git a/packages/babel-generator/src/generators/flow.js b/packages/babel-generator/src/generators/flow.js
index 75a1147535..2aa5acb939 100644
--- a/packages/babel-generator/src/generators/flow.js
+++ b/packages/babel-generator/src/generators/flow.js
@@ -384,6 +384,7 @@ export function ObjectTypeAnnotation(node: Object) {
   const props = node.properties.concat(
     node.callProperties || [],
     node.indexers || [],
+    node.internalSlots || [],
   );
 
   if (props.length) {
@@ -413,6 +414,23 @@ export function ObjectTypeAnnotation(node: Object) {
   }
 }
 
+export function ObjectTypeInternalSlot(node: Object) {
+  if (node.static) {
+    this.word("static");
+    this.space();
+  }
+  this.token("[");
+  this.token("[");
+  this.print(node.id, node);
+  this.token("]");
+  this.token("]");
+  if (!node.method) {
+    this.token(":");
+    this.space();
+  }
+  this.print(node.value, node);
+}
+
 export function ObjectTypeCallProperty(node: Object) {
   if (node.static) {
     this.word("static");
diff --git a/packages/babel-generator/src/node/whitespace.js b/packages/babel-generator/src/node/whitespace.js
index ecc467b6cf..c9bf14750d 100644
--- a/packages/babel-generator/src/node/whitespace.js
+++ b/packages/babel-generator/src/node/whitespace.js
@@ -209,6 +209,22 @@ nodes.ObjectTypeIndexer = function(node: Object, parent): ?WhitespaceObject {
   }
 };
 
+nodes.ObjectTypeInternalSlot = function(
+  node: Object,
+  parent,
+): ?WhitespaceObject {
+  if (
+    parent.internalSlots[0] === node &&
+    (!parent.properties || !parent.properties.length) &&
+    (!parent.callProperties || !parent.callProperties.length) &&
+    (!parent.indexers || !parent.indexers.length)
+  ) {
+    return {
+      before: true,
+    };
+  }
+};
+
 /**
  * Returns lists from node types that need whitespace.
  */
diff --git a/packages/babel-generator/test/fixtures/flow/internal-slot/input.js b/packages/babel-generator/test/fixtures/flow/internal-slot/input.js
new file mode 100644
index 0000000000..e26a0046be
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/flow/internal-slot/input.js
@@ -0,0 +1,6 @@
+declare class C { static [[foo]]: T }
+declare class C { [[foo]]: T }
+interface T { [[foo]]: X }
+interface T { [[foo]](): X }
+type T = { [[foo]]: X }
+type T = { [[foo]](): X }
diff --git a/packages/babel-generator/test/fixtures/flow/internal-slot/output.js b/packages/babel-generator/test/fixtures/flow/internal-slot/output.js
new file mode 100644
index 0000000000..61a87ea113
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/flow/internal-slot/output.js
@@ -0,0 +1,18 @@
+declare class C {
+  static [[foo]]: T
+}
+declare class C {
+  [[foo]]: T
+}
+interface T {
+  [[foo]]: X
+}
+interface T {
+  [[foo]]() => X
+}
+type T = {
+  [[foo]]: X
+};
+type T = {
+  [[foo]]() => X
+};
\ No newline at end of file
diff --git a/packages/babel-generator/test/index.js b/packages/babel-generator/test/index.js
index 9b71e3311f..f09e4f091f 100644
--- a/packages/babel-generator/test/index.js
+++ b/packages/babel-generator/test/index.js
@@ -304,6 +304,7 @@ describe("programmatic generation", function() {
       [t.objectTypeProperty(t.identifier("bar"), t.stringTypeAnnotation())],
       null,
       null,
+      null,
     );
 
     const output = generate(objectStatement).code;
@@ -317,6 +318,7 @@ describe("programmatic generation", function() {
       [t.objectTypeProperty(t.identifier("bar"), t.stringTypeAnnotation())],
       null,
       null,
+      null,
       true,
     );
 
@@ -336,6 +338,7 @@ describe("programmatic generation", function() {
           t.numberTypeAnnotation(),
         ),
       ],
+      null,
     );
 
     const output = generate(objectStatement).code;
diff --git a/packages/babel-types/src/definitions/flow.js b/packages/babel-types/src/definitions/flow.js
index 5d58b24681..caf33c2c9e 100644
--- a/packages/babel-types/src/definitions/flow.js
+++ b/packages/babel-types/src/definitions/flow.js
@@ -248,15 +248,22 @@ defineType("NumberTypeAnnotation", {
 });
 
 defineType("ObjectTypeAnnotation", {
-  visitor: ["properties", "indexers", "callProperties"],
+  visitor: ["properties", "indexers", "callProperties", "internalSlots"],
   aliases: ["Flow", "FlowType"],
-  builder: ["properties", "indexers", "callProperties", "exact"],
+  builder: [
+    "properties",
+    "indexers",
+    "callProperties",
+    "internalSlots",
+    "exact",
+  ],
   fields: {
     properties: validate(
       arrayOfType(["ObjectTypeProperty", "ObjectTypeSpreadProperty"]),
     ),
     indexers: validateOptional(arrayOfType("ObjectTypeIndexer")),
     callProperties: validateOptional(arrayOfType("ObjectTypeCallProperty")),
+    internalSlots: validateOptional(arrayOfType("ObjectTypeInternalSlot")),
     exact: {
       validate: assertValueType("boolean"),
       default: false,
@@ -264,6 +271,17 @@ defineType("ObjectTypeAnnotation", {
   },
 });
 
+defineType("ObjectTypeInternalSlot", {
+  visitor: ["id", "value", "static", "method"],
+  aliases: ["Flow", "UserWhitespacable"],
+  fields: {
+    id: validateType("Identifier"),
+    value: validateType("FlowType"),
+    static: validate(assertValueType("boolean")),
+    method: validate(assertValueType("boolean")),
+  },
+});
+
 defineType("ObjectTypeCallProperty", {
   visitor: ["value"],
   aliases: ["Flow", "UserWhitespacable"],
diff --git a/packages/babylon/src/plugins/flow.js b/packages/babylon/src/plugins/flow.js
index caa347207b..ddc81e9484 100644
--- a/packages/babylon/src/plugins/flow.js
+++ b/packages/babylon/src/plugins/flow.js
@@ -621,7 +621,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     ): N.FlowObjectTypeIndexer {
       node.static = isStatic;
 
-      this.expect(tt.bracketL);
+      // Note: bracketL has already been consumed
       if (this.lookahead().type === tt.colon) {
         node.id = this.flowParseObjectPropertyKey();
         node.key = this.flowParseTypeInitialiser();
@@ -636,6 +636,27 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return this.finishNode(node, "ObjectTypeIndexer");
     }
 
+    flowParseObjectTypeInternalSlot(
+      node: N.FlowObjectTypeInternalSlot,
+      isStatic: boolean,
+    ): N.FlowObjectTypeInternalSlot {
+      node.static = isStatic;
+      // Note: both bracketL have already been consumed
+      node.id = this.flowParseObjectPropertyKey();
+      this.expect(tt.bracketR);
+      this.expect(tt.bracketR);
+      if (this.isRelational("<") || this.match(tt.parenL)) {
+        node.method = true;
+        node.value = this.flowParseObjectTypeMethodish(
+          this.startNodeAt(node.start, node.loc.start),
+        );
+      } else {
+        node.method = false;
+        node.value = this.flowParseTypeInitialiser();
+      }
+      return this.finishNode(node, "ObjectTypeInternalSlot");
+    }
+
     flowParseObjectTypeMethodish(
       node: N.FlowFunctionTypeAnnotation,
     ): N.FlowFunctionTypeAnnotation {
@@ -689,6 +710,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       nodeStart.callProperties = [];
       nodeStart.properties = [];
       nodeStart.indexers = [];
+      nodeStart.internalSlots = [];
 
       let endDelim;
       let exact;
@@ -720,10 +742,19 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
         const variance = this.flowParseVariance();
 
-        if (this.match(tt.bracketL)) {
-          nodeStart.indexers.push(
-            this.flowParseObjectTypeIndexer(node, isStatic, variance),
-          );
+        if (this.eat(tt.bracketL)) {
+          if (this.eat(tt.bracketL)) {
+            if (variance) {
+              this.unexpected(variance.start);
+            }
+            nodeStart.internalSlots.push(
+              this.flowParseObjectTypeInternalSlot(node, isStatic),
+            );
+          } else {
+            nodeStart.indexers.push(
+              this.flowParseObjectTypeIndexer(node, isStatic, variance),
+            );
+          }
         } else if (this.match(tt.parenL) || this.isRelational("<")) {
           if (variance) {
             this.unexpected(variance.start);
diff --git a/packages/babylon/src/types.js b/packages/babylon/src/types.js
index ee9bd93631..91a1535d7f 100644
--- a/packages/babylon/src/types.js
+++ b/packages/babylon/src/types.js
@@ -915,6 +915,7 @@ export type FlowInterfaceExtends = Node;
 export type FlowTypeAlias = Node;
 export type FlowOpaqueType = Node;
 export type FlowObjectTypeIndexer = Node;
+export type FlowObjectTypeInternalSlot = Node;
 export type FlowFunctionTypeAnnotation = Node;
 export type FlowObjectTypeProperty = Node;
 export type FlowObjectTypeSpreadProperty = Node;
diff --git a/packages/babylon/test/fixtures/flow/call-properties/1/output.json b/packages/babylon/test/fixtures/flow/call-properties/1/output.json
index 6ea3d1e4bb..a8f731da4a 100644
--- a/packages/babylon/test/fixtures/flow/call-properties/1/output.json
+++ b/packages/babylon/test/fixtures/flow/call-properties/1/output.json
@@ -154,6 +154,7 @@
                   ],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/call-properties/2/output.json b/packages/babylon/test/fixtures/flow/call-properties/2/output.json
index 87148b542a..af04ce04dd 100644
--- a/packages/babylon/test/fixtures/flow/call-properties/2/output.json
+++ b/packages/babylon/test/fixtures/flow/call-properties/2/output.json
@@ -154,6 +154,7 @@
                   ],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/call-properties/3/output.json b/packages/babylon/test/fixtures/flow/call-properties/3/output.json
index fdc92e6b2b..2455ef16d7 100644
--- a/packages/babylon/test/fixtures/flow/call-properties/3/output.json
+++ b/packages/babylon/test/fixtures/flow/call-properties/3/output.json
@@ -305,6 +305,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/call-properties/4/output.json b/packages/babylon/test/fixtures/flow/call-properties/4/output.json
index 08e9c26694..98ed1c12e8 100644
--- a/packages/babylon/test/fixtures/flow/call-properties/4/output.json
+++ b/packages/babylon/test/fixtures/flow/call-properties/4/output.json
@@ -254,6 +254,7 @@
                   ],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/call-properties/5/output.json b/packages/babylon/test/fixtures/flow/call-properties/5/output.json
index 306d17dc8c..c7b8b89bf7 100644
--- a/packages/babylon/test/fixtures/flow/call-properties/5/output.json
+++ b/packages/babylon/test/fixtures/flow/call-properties/5/output.json
@@ -130,6 +130,7 @@
           ],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/class-properties/getter-setter/output.json b/packages/babylon/test/fixtures/flow/class-properties/getter-setter/output.json
index 9439a28902..a62d033d1a 100644
--- a/packages/babylon/test/fixtures/flow/class-properties/getter-setter/output.json
+++ b/packages/babylon/test/fixtures/flow/class-properties/getter-setter/output.json
@@ -654,6 +654,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/class-properties/named-static/output.json b/packages/babylon/test/fixtures/flow/class-properties/named-static/output.json
index cb362f9359..d42ce47484 100644
--- a/packages/babylon/test/fixtures/flow/class-properties/named-static/output.json
+++ b/packages/babylon/test/fixtures/flow/class-properties/named-static/output.json
@@ -151,6 +151,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/comment/02-type-include/output.json b/packages/babylon/test/fixtures/flow/comment/02-type-include/output.json
index bd476ff5d7..8f95c43077 100644
--- a/packages/babylon/test/fixtures/flow/comment/02-type-include/output.json
+++ b/packages/babylon/test/fixtures/flow/comment/02-type-include/output.json
@@ -234,6 +234,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/comment/03-type-flow-include/output.json b/packages/babylon/test/fixtures/flow/comment/03-type-flow-include/output.json
index 05a7bcd068..4d0155be57 100644
--- a/packages/babylon/test/fixtures/flow/comment/03-type-flow-include/output.json
+++ b/packages/babylon/test/fixtures/flow/comment/03-type-flow-include/output.json
@@ -234,6 +234,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-class/implements-multiple/output.json b/packages/babylon/test/fixtures/flow/declare-class/implements-multiple/output.json
index d542929729..9aae9f3dfb 100644
--- a/packages/babylon/test/fixtures/flow/declare-class/implements-multiple/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-class/implements-multiple/output.json
@@ -147,6 +147,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-class/implements-with-mixin/output.json b/packages/babylon/test/fixtures/flow/declare-class/implements-with-mixin/output.json
index 90a3ce2742..b7420ee2bb 100644
--- a/packages/babylon/test/fixtures/flow/declare-class/implements-with-mixin/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-class/implements-with-mixin/output.json
@@ -148,6 +148,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-class/implements/output.json b/packages/babylon/test/fixtures/flow/declare-class/implements/output.json
index 2b6e2f9226..147cd4723c 100644
--- a/packages/babylon/test/fixtures/flow/declare-class/implements/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-class/implements/output.json
@@ -114,6 +114,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-class/mixins-multiple/output.json b/packages/babylon/test/fixtures/flow/declare-class/mixins-multiple/output.json
index 2e0c40e321..0cc7bb6f63 100644
--- a/packages/babylon/test/fixtures/flow/declare-class/mixins-multiple/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-class/mixins-multiple/output.json
@@ -147,6 +147,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-class/mixins/output.json b/packages/babylon/test/fixtures/flow/declare-class/mixins/output.json
index 4dc1aceddf..976666c5aa 100644
--- a/packages/babylon/test/fixtures/flow/declare-class/mixins/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-class/mixins/output.json
@@ -114,6 +114,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-export/export-class/output.json b/packages/babylon/test/fixtures/flow/declare-export/export-class/output.json
index 98d369c164..0c677c578e 100644
--- a/packages/babylon/test/fixtures/flow/declare-export/export-class/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-export/export-class/output.json
@@ -262,6 +262,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               },
diff --git a/packages/babylon/test/fixtures/flow/declare-export/export-default-class/output.json b/packages/babylon/test/fixtures/flow/declare-export/export-default-class/output.json
index 61983df103..d61334fe3e 100644
--- a/packages/babylon/test/fixtures/flow/declare-export/export-default-class/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-export/export-default-class/output.json
@@ -94,6 +94,7 @@
             "callProperties": [],
             "properties": [],
             "indexers": [],
+            "internalSlots": [],
             "exact": false
           }
         },
diff --git a/packages/babylon/test/fixtures/flow/declare-export/export-interface-and-var/output.json b/packages/babylon/test/fixtures/flow/declare-export/export-interface-and-var/output.json
index a5e525c737..afda6a4c4f 100644
--- a/packages/babylon/test/fixtures/flow/declare-export/export-interface-and-var/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-export/export-interface-and-var/output.json
@@ -145,6 +145,7 @@
                   "callProperties": [],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               },
diff --git a/packages/babylon/test/fixtures/flow/declare-export/export-interface-commonjs/output.json b/packages/babylon/test/fixtures/flow/declare-export/export-interface-commonjs/output.json
index 39e702dea8..ef1c280b06 100644
--- a/packages/babylon/test/fixtures/flow/declare-export/export-interface-commonjs/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-export/export-interface-commonjs/output.json
@@ -145,6 +145,7 @@
                   "callProperties": [],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               },
diff --git a/packages/babylon/test/fixtures/flow/declare-export/export-interface/output.json b/packages/babylon/test/fixtures/flow/declare-export/export-interface/output.json
index 423ce5adf1..e174a6e56d 100644
--- a/packages/babylon/test/fixtures/flow/declare-export/export-interface/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-export/export-interface/output.json
@@ -145,6 +145,7 @@
                   "callProperties": [],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               },
diff --git a/packages/babylon/test/fixtures/flow/declare-module/10/output.json b/packages/babylon/test/fixtures/flow/declare-module/10/output.json
index 36bd707144..8af394d53a 100644
--- a/packages/babylon/test/fixtures/flow/declare-module/10/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-module/10/output.json
@@ -143,6 +143,7 @@
               }
             ],
             "indexers": [],
+            "internalSlots": [],
             "exact": false
           }
         }
diff --git a/packages/babylon/test/fixtures/flow/declare-module/5/output.json b/packages/babylon/test/fixtures/flow/declare-module/5/output.json
index 5ce1498f42..cca82df7c2 100644
--- a/packages/babylon/test/fixtures/flow/declare-module/5/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-module/5/output.json
@@ -196,6 +196,7 @@
                   }
                 ],
                 "indexers": [],
+                "internalSlots": [],
                 "exact": false
               }
             }
diff --git a/packages/babylon/test/fixtures/flow/declare-module/6/output.json b/packages/babylon/test/fixtures/flow/declare-module/6/output.json
index c96803274c..2f3709e3c8 100644
--- a/packages/babylon/test/fixtures/flow/declare-module/6/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-module/6/output.json
@@ -189,6 +189,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/10/output.json b/packages/babylon/test/fixtures/flow/declare-statements/10/output.json
index 1bcf3e6e9e..7e7e652c21 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/10/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/10/output.json
@@ -202,6 +202,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/11/output.json b/packages/babylon/test/fixtures/flow/declare-statements/11/output.json
index 5c95cf2a5b..8c33bf543c 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/11/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/11/output.json
@@ -145,6 +145,7 @@
               "variance": null
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/12/output.json b/packages/babylon/test/fixtures/flow/declare-statements/12/output.json
index 4460f260fb..388654aa76 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/12/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/12/output.json
@@ -130,6 +130,7 @@
           ],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/13/output.json b/packages/babylon/test/fixtures/flow/declare-statements/13/output.json
index b9f0125e9a..a39f0dea7f 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/13/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/13/output.json
@@ -196,6 +196,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/14/output.json b/packages/babylon/test/fixtures/flow/declare-statements/14/output.json
index ea11ee2d77..1f59abdb8e 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/14/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/14/output.json
@@ -241,6 +241,7 @@
               "variance": null
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/15/output.json b/packages/babylon/test/fixtures/flow/declare-statements/15/output.json
index 3208fef5b5..e7e3eb938d 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/15/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/15/output.json
@@ -133,6 +133,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       },
@@ -292,6 +293,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/16/output.json b/packages/babylon/test/fixtures/flow/declare-statements/16/output.json
index 68a1978b51..d6199249d8 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/16/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/16/output.json
@@ -178,6 +178,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/17/output.json b/packages/babylon/test/fixtures/flow/declare-statements/17/output.json
index 3279562c14..13cddb011a 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/17/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/17/output.json
@@ -237,6 +237,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/18/output.json b/packages/babylon/test/fixtures/flow/declare-statements/18/output.json
index 3c4cd37283..40bbec8261 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/18/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/18/output.json
@@ -130,6 +130,7 @@
           ],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       },
@@ -235,6 +236,7 @@
           ],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/7/output.json b/packages/babylon/test/fixtures/flow/declare-statements/7/output.json
index 57e98a51ee..fc43fe1bee 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/7/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/7/output.json
@@ -265,6 +265,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/8/output.json b/packages/babylon/test/fixtures/flow/declare-statements/8/output.json
index 9ae134f7ae..0a000e7baf 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/8/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/8/output.json
@@ -80,6 +80,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/declare-statements/9/output.json b/packages/babylon/test/fixtures/flow/declare-statements/9/output.json
index 757e446721..152a0c09bf 100644
--- a/packages/babylon/test/fixtures/flow/declare-statements/9/output.json
+++ b/packages/babylon/test/fixtures/flow/declare-statements/9/output.json
@@ -249,6 +249,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/def-site-variance/1/output.json b/packages/babylon/test/fixtures/flow/def-site-variance/1/output.json
index 5f77fd7ae9..9deb99b68b 100644
--- a/packages/babylon/test/fixtures/flow/def-site-variance/1/output.json
+++ b/packages/babylon/test/fixtures/flow/def-site-variance/1/output.json
@@ -420,6 +420,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/1/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/1/output.json
index 2ea75fd807..0f6a20ca9f 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/1/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/1/output.json
@@ -80,6 +80,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/10/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/10/output.json
index 8bebb8ba55..0ee88d1a87 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/10/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/10/output.json
@@ -235,6 +235,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/2/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/2/output.json
index eb8ac60e38..695fffdf93 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/2/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/2/output.json
@@ -114,6 +114,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/3/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/3/output.json
index 9212a82374..54b8851e9a 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/3/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/3/output.json
@@ -278,6 +278,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/4/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/4/output.json
index 2705283764..e10d0594bf 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/4/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/4/output.json
@@ -151,6 +151,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/5/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/5/output.json
index 2114abd4bf..7bf080c87b 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/5/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/5/output.json
@@ -198,6 +198,7 @@
               "variance": null
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/id-reserved-value/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/id-reserved-value/output.json
index 2fc2a10be8..980569d6bd 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/id-reserved-value/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/id-reserved-value/output.json
@@ -80,6 +80,7 @@
           "callProperties": [],
           "properties": [],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/identifier-named-static-optional/output.json b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/identifier-named-static-optional/output.json
index 036b95cb86..b035f457ed 100644
--- a/packages/babylon/test/fixtures/flow/interfaces-module-and-script/identifier-named-static-optional/output.json
+++ b/packages/babylon/test/fixtures/flow/interfaces-module-and-script/identifier-named-static-optional/output.json
@@ -133,6 +133,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/input.js b/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/input.js
new file mode 100644
index 0000000000..9ae853ad62
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/input.js
@@ -0,0 +1 @@
+declare class C { static [[foo]]: T }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/output.json b/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/output.json
new file mode 100644
index 0000000000..fd51f274b3
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/declare-class-static/output.json
@@ -0,0 +1,158 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 37,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 37
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 37,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 37
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "DeclareClass",
+        "start": 0,
+        "end": 37,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 37
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 14,
+          "end": 15,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 14
+            },
+            "end": {
+              "line": 1,
+              "column": 15
+            },
+            "identifierName": "C"
+          },
+          "name": "C"
+        },
+        "typeParameters": null,
+        "extends": [],
+        "implements": [],
+        "mixins": [],
+        "body": {
+          "type": "ObjectTypeAnnotation",
+          "start": 16,
+          "end": 37,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 16
+            },
+            "end": {
+              "line": 1,
+              "column": 37
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 18,
+              "end": 35,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 18
+                },
+                "end": {
+                  "line": 1,
+                  "column": 35
+                }
+              },
+              "static": true,
+              "id": {
+                "type": "Identifier",
+                "start": 27,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 27
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 30
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": false,
+              "value": {
+                "type": "GenericTypeAnnotation",
+                "start": 34,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 34
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 35
+                  }
+                },
+                "typeParameters": null,
+                "id": {
+                  "type": "Identifier",
+                  "start": 34,
+                  "end": 35,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 34
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 35
+                    },
+                    "identifierName": "T"
+                  },
+                  "name": "T"
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/declare-class/input.js b/packages/babylon/test/fixtures/flow/internal-slot/declare-class/input.js
new file mode 100644
index 0000000000..24dd359b9e
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/declare-class/input.js
@@ -0,0 +1 @@
+declare class C { [[foo]]: T }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/declare-class/output.json b/packages/babylon/test/fixtures/flow/internal-slot/declare-class/output.json
new file mode 100644
index 0000000000..30b1ff1fe9
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/declare-class/output.json
@@ -0,0 +1,158 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 30,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 30
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 30,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 30
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "DeclareClass",
+        "start": 0,
+        "end": 30,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 30
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 14,
+          "end": 15,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 14
+            },
+            "end": {
+              "line": 1,
+              "column": 15
+            },
+            "identifierName": "C"
+          },
+          "name": "C"
+        },
+        "typeParameters": null,
+        "extends": [],
+        "implements": [],
+        "mixins": [],
+        "body": {
+          "type": "ObjectTypeAnnotation",
+          "start": 16,
+          "end": 30,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 16
+            },
+            "end": {
+              "line": 1,
+              "column": 30
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 18,
+              "end": 28,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 18
+                },
+                "end": {
+                  "line": 1,
+                  "column": 28
+                }
+              },
+              "static": false,
+              "id": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 20
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 23
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": false,
+              "value": {
+                "type": "GenericTypeAnnotation",
+                "start": 27,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 27
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 28
+                  }
+                },
+                "typeParameters": null,
+                "id": {
+                  "type": "Identifier",
+                  "start": 27,
+                  "end": 28,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 27
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 28
+                    },
+                    "identifierName": "T"
+                  },
+                  "name": "T"
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface-method/input.js b/packages/babylon/test/fixtures/flow/internal-slot/interface-method/input.js
new file mode 100644
index 0000000000..ce9f3e4872
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface-method/input.js
@@ -0,0 +1 @@
+interface T { [[foo]](): X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface-method/output.json b/packages/babylon/test/fixtures/flow/internal-slot/interface-method/output.json
new file mode 100644
index 0000000000..83ec869b9a
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface-method/output.json
@@ -0,0 +1,176 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 28,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 28
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 28,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 28
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "InterfaceDeclaration",
+        "start": 0,
+        "end": 28,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 28
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 10,
+          "end": 11,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 10
+            },
+            "end": {
+              "line": 1,
+              "column": 11
+            },
+            "identifierName": "T"
+          },
+          "name": "T"
+        },
+        "typeParameters": null,
+        "extends": [],
+        "implements": [],
+        "mixins": [],
+        "body": {
+          "type": "ObjectTypeAnnotation",
+          "start": 12,
+          "end": 28,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 12
+            },
+            "end": {
+              "line": 1,
+              "column": 28
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 14,
+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 14
+                },
+                "end": {
+                  "line": 1,
+                  "column": 26
+                }
+              },
+              "static": false,
+              "id": {
+                "type": "Identifier",
+                "start": 16,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 16
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 19
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": true,
+              "value": {
+                "type": "FunctionTypeAnnotation",
+                "start": 14,
+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 26
+                  }
+                },
+                "params": [],
+                "rest": null,
+                "typeParameters": null,
+                "returnType": {
+                  "type": "GenericTypeAnnotation",
+                  "start": 25,
+                  "end": 26,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 25
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 26
+                    }
+                  },
+                  "typeParameters": null,
+                  "id": {
+                    "type": "Identifier",
+                    "start": 25,
+                    "end": 26,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 25
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 26
+                      },
+                      "identifierName": "X"
+                    },
+                    "name": "X"
+                  }
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/input.js b/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/input.js
new file mode 100644
index 0000000000..2c51c5464e
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/input.js
@@ -0,0 +1 @@
+interface T { +[[foo]](): X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/options.json b/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/options.json
new file mode 100644
index 0000000000..d50e8469b8
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface-variance/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token (1:14)"
+}
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface/input.js b/packages/babylon/test/fixtures/flow/internal-slot/interface/input.js
new file mode 100644
index 0000000000..ce1d513db5
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface/input.js
@@ -0,0 +1 @@
+interface T { [[foo]]: X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/interface/output.json b/packages/babylon/test/fixtures/flow/internal-slot/interface/output.json
new file mode 100644
index 0000000000..bb9031963c
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/interface/output.json
@@ -0,0 +1,158 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 26,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 26
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 26,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 26
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "InterfaceDeclaration",
+        "start": 0,
+        "end": 26,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 26
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 10,
+          "end": 11,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 10
+            },
+            "end": {
+              "line": 1,
+              "column": 11
+            },
+            "identifierName": "T"
+          },
+          "name": "T"
+        },
+        "typeParameters": null,
+        "extends": [],
+        "implements": [],
+        "mixins": [],
+        "body": {
+          "type": "ObjectTypeAnnotation",
+          "start": 12,
+          "end": 26,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 12
+            },
+            "end": {
+              "line": 1,
+              "column": 26
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 14,
+              "end": 24,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 14
+                },
+                "end": {
+                  "line": 1,
+                  "column": 24
+                }
+              },
+              "static": false,
+              "id": {
+                "type": "Identifier",
+                "start": 16,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 16
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 19
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": false,
+              "value": {
+                "type": "GenericTypeAnnotation",
+                "start": 23,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 23
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 24
+                  }
+                },
+                "typeParameters": null,
+                "id": {
+                  "type": "Identifier",
+                  "start": 23,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 23
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 24
+                    },
+                    "identifierName": "X"
+                  },
+                  "name": "X"
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object-method/input.js b/packages/babylon/test/fixtures/flow/internal-slot/object-method/input.js
new file mode 100644
index 0000000000..193e329a1c
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object-method/input.js
@@ -0,0 +1 @@
+type T = { [[foo]](): X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object-method/output.json b/packages/babylon/test/fixtures/flow/internal-slot/object-method/output.json
new file mode 100644
index 0000000000..a27cbbf6a2
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object-method/output.json
@@ -0,0 +1,173 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 25,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 25
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 25,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 25
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "TypeAlias",
+        "start": 0,
+        "end": 25,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 25
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 5,
+          "end": 6,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 5
+            },
+            "end": {
+              "line": 1,
+              "column": 6
+            },
+            "identifierName": "T"
+          },
+          "name": "T"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "ObjectTypeAnnotation",
+          "start": 9,
+          "end": 25,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 9
+            },
+            "end": {
+              "line": 1,
+              "column": 25
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 11,
+              "end": 23,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 11
+                },
+                "end": {
+                  "line": 1,
+                  "column": 23
+                }
+              },
+              "static": false,
+              "id": {
+                "type": "Identifier",
+                "start": 13,
+                "end": 16,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 16
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": true,
+              "value": {
+                "type": "FunctionTypeAnnotation",
+                "start": 11,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 23
+                  }
+                },
+                "params": [],
+                "rest": null,
+                "typeParameters": null,
+                "returnType": {
+                  "type": "GenericTypeAnnotation",
+                  "start": 22,
+                  "end": 23,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 22
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 23
+                    }
+                  },
+                  "typeParameters": null,
+                  "id": {
+                    "type": "Identifier",
+                    "start": 22,
+                    "end": 23,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 22
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 23
+                      },
+                      "identifierName": "X"
+                    },
+                    "name": "X"
+                  }
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object-variance/input.js b/packages/babylon/test/fixtures/flow/internal-slot/object-variance/input.js
new file mode 100644
index 0000000000..9e5318f912
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object-variance/input.js
@@ -0,0 +1 @@
+type T = { +[[foo]]: X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object-variance/options.json b/packages/babylon/test/fixtures/flow/internal-slot/object-variance/options.json
new file mode 100644
index 0000000000..cb6c66081e
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object-variance/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token (1:11)"
+}
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object/input.js b/packages/babylon/test/fixtures/flow/internal-slot/object/input.js
new file mode 100644
index 0000000000..6601e90896
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object/input.js
@@ -0,0 +1 @@
+type T = { [[foo]]: X }
diff --git a/packages/babylon/test/fixtures/flow/internal-slot/object/output.json b/packages/babylon/test/fixtures/flow/internal-slot/object/output.json
new file mode 100644
index 0000000000..002d1abdfe
--- /dev/null
+++ b/packages/babylon/test/fixtures/flow/internal-slot/object/output.json
@@ -0,0 +1,155 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 23,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 23
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 23,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 23
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "TypeAlias",
+        "start": 0,
+        "end": 23,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 23
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 5,
+          "end": 6,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 5
+            },
+            "end": {
+              "line": 1,
+              "column": 6
+            },
+            "identifierName": "T"
+          },
+          "name": "T"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "ObjectTypeAnnotation",
+          "start": 9,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 9
+            },
+            "end": {
+              "line": 1,
+              "column": 23
+            }
+          },
+          "callProperties": [],
+          "properties": [],
+          "indexers": [],
+          "internalSlots": [
+            {
+              "type": "ObjectTypeInternalSlot",
+              "start": 11,
+              "end": 21,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 11
+                },
+                "end": {
+                  "line": 1,
+                  "column": 21
+                }
+              },
+              "static": false,
+              "id": {
+                "type": "Identifier",
+                "start": 13,
+                "end": 16,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 16
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "method": false,
+              "value": {
+                "type": "GenericTypeAnnotation",
+                "start": 20,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 20
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 21
+                  }
+                },
+                "typeParameters": null,
+                "id": {
+                  "type": "Identifier",
+                  "start": 20,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 20
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 21
+                    },
+                    "identifierName": "X"
+                  },
+                  "name": "X"
+                }
+              }
+            }
+          ],
+          "exact": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/flow/iterator/01/output.json b/packages/babylon/test/fixtures/flow/iterator/01/output.json
index 3275f3a0b9..e12e269720 100644
--- a/packages/babylon/test/fixtures/flow/iterator/01/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/01/output.json
@@ -217,6 +217,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/iterator/02/output.json b/packages/babylon/test/fixtures/flow/iterator/02/output.json
index 8d0a7d2c0f..8d4891d72d 100644
--- a/packages/babylon/test/fixtures/flow/iterator/02/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/02/output.json
@@ -217,6 +217,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/iterator/12/output.json b/packages/babylon/test/fixtures/flow/iterator/12/output.json
index c599c26962..c0a408e78c 100644
--- a/packages/babylon/test/fixtures/flow/iterator/12/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/12/output.json
@@ -165,6 +165,7 @@
               }
             ],
             "indexers": [],
+            "internalSlots": [],
             "exact": false
           }
         },
diff --git a/packages/babylon/test/fixtures/flow/iterator/13/output.json b/packages/babylon/test/fixtures/flow/iterator/13/output.json
index 43ac1dab55..ff95cf2628 100644
--- a/packages/babylon/test/fixtures/flow/iterator/13/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/13/output.json
@@ -165,6 +165,7 @@
               }
             ],
             "indexers": [],
+            "internalSlots": [],
             "exact": false
           }
         },
diff --git a/packages/babylon/test/fixtures/flow/iterator/14/output.json b/packages/babylon/test/fixtures/flow/iterator/14/output.json
index 78e416e067..3403c5ce09 100644
--- a/packages/babylon/test/fixtures/flow/iterator/14/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/14/output.json
@@ -217,6 +217,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/iterator/15/output.json b/packages/babylon/test/fixtures/flow/iterator/15/output.json
index 02ed08c46b..c5c9e4032e 100644
--- a/packages/babylon/test/fixtures/flow/iterator/15/output.json
+++ b/packages/babylon/test/fixtures/flow/iterator/15/output.json
@@ -217,6 +217,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/object-types/complex-param-types/output.json b/packages/babylon/test/fixtures/flow/object-types/complex-param-types/output.json
index f74a8e1c53..617fe340fa 100644
--- a/packages/babylon/test/fixtures/flow/object-types/complex-param-types/output.json
+++ b/packages/babylon/test/fixtures/flow/object-types/complex-param-types/output.json
@@ -230,6 +230,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-alias/4/output.json b/packages/babylon/test/fixtures/flow/type-alias/4/output.json
index 549a3e9f02..69682ac3f3 100644
--- a/packages/babylon/test/fixtures/flow/type-alias/4/output.json
+++ b/packages/babylon/test/fixtures/flow/type-alias/4/output.json
@@ -150,6 +150,7 @@
                 }
               ],
               "indexers": [],
+              "internalSlots": [],
               "exact": false
             },
             {
@@ -227,6 +228,7 @@
                 }
               ],
               "indexers": [],
+              "internalSlots": [],
               "exact": false
             }
           ]
@@ -618,6 +620,7 @@
                       }
                     ],
                     "indexers": [],
+                    "internalSlots": [],
                     "exact": false
                   },
                   {
@@ -695,6 +698,7 @@
                       }
                     ],
                     "indexers": [],
+                    "internalSlots": [],
                     "exact": false
                   }
                 ]
@@ -704,6 +708,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       },
@@ -879,6 +884,7 @@
                       }
                     ],
                     "indexers": [],
+                    "internalSlots": [],
                     "exact": false
                   },
                   {
@@ -956,6 +962,7 @@
                       }
                     ],
                     "indexers": [],
+                    "internalSlots": [],
                     "exact": false
                   }
                 ]
@@ -965,6 +972,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/108/output.json b/packages/babylon/test/fixtures/flow/type-annotations/108/output.json
index 635352a145..a5dd5fc694 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/108/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/108/output.json
@@ -209,6 +209,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": true
                 }
               }
@@ -525,6 +526,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": true
                 }
               }
@@ -736,6 +738,7 @@
                   "callProperties": [],
                   "properties": [],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": true
                 }
               }
@@ -991,6 +994,7 @@
                           }
                         ],
                         "indexers": [],
+                        "internalSlots": [],
                         "exact": true
                       },
                       "variance": null,
@@ -1050,6 +1054,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": false
                 }
               }
@@ -1519,6 +1524,7 @@
                           }
                         ],
                         "indexers": [],
+                        "internalSlots": [],
                         "exact": false
                       },
                       "variance": null,
@@ -1578,6 +1584,7 @@
                     }
                   ],
                   "indexers": [],
+                  "internalSlots": [],
                   "exact": true
                 }
               }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/110/output.json b/packages/babylon/test/fixtures/flow/type-annotations/110/output.json
index 5942b598e2..1dd92b8c0b 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/110/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/110/output.json
@@ -163,6 +163,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/111/output.json b/packages/babylon/test/fixtures/flow/type-annotations/111/output.json
index 4b3f7042a0..2cc443b0bf 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/111/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/111/output.json
@@ -163,6 +163,7 @@
             }
           ],
           "indexers": [],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/114/output.json b/packages/babylon/test/fixtures/flow/type-annotations/114/output.json
index 5cbe3ec43a..1c33baf64c 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/114/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/114/output.json
@@ -193,6 +193,7 @@
               }
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/115/output.json b/packages/babylon/test/fixtures/flow/type-annotations/115/output.json
index cdb32af1e6..82eb32ad8a 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/115/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/115/output.json
@@ -193,6 +193,7 @@
               }
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/127/output.json b/packages/babylon/test/fixtures/flow/type-annotations/127/output.json
index c9361209da..175daf7287 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/127/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/127/output.json
@@ -126,6 +126,7 @@
               "variance": null
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/128/output.json b/packages/babylon/test/fixtures/flow/type-annotations/128/output.json
index 76203fc324..ef8de3380b 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/128/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/128/output.json
@@ -158,6 +158,7 @@
               "variance": null
             }
           ],
+          "internalSlots": [],
           "exact": false
         }
       }
diff --git a/packages/babylon/test/fixtures/flow/type-annotations/135/output.json b/packages/babylon/test/fixtures/flow/type-annotations/135/output.json
index 14027b107e..639a96cd00 100644
--- a/packages/babylon/test/fixtures/flow/type-annotations/135/output.json
+++ b/packages/babylon/test/fixtures/flow/type-annotations/135/output.json
@@ -108,6 +108,7 @@
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index 3033b68e37..6e107d565a 100644
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diff --git a/packages/babylon/test/fixtures/flow/type-exports/interface/output.json b/packages/babylon/test/fixtures/flow/type-exports/interface/output.json
index f8cc2f9749..8f59babc94 100644
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@@ -150,6 +150,7 @@
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index 21c1ee39f8..eefea8c54a 100644
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index c38e1e5f03..1d39fe9b29 100644
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index 2811767bec..933d7973df 100644
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@@ -486,6 +486,7 @@
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diff --git a/packages/babylon/test/fixtures/flow/typecasts/2/output.json b/packages/babylon/test/fixtures/flow/typecasts/2/output.json
index c42819ddfe..fa7eef5b04 100644
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@@ -319,6 +319,7 @@
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diff --git a/scripts/tests/flow/flow_tests_whitelist.txt b/scripts/tests/flow/flow_tests_whitelist.txt
index 322247aa30..74d9819c0d 100644
--- a/scripts/tests/flow/flow_tests_whitelist.txt
+++ b/scripts/tests/flow/flow_tests_whitelist.txt
@@ -31,9 +31,6 @@ types/member/reserved_words.js
 types/parameter_defaults/migrated_0032.js
 types/typecasts_invalid/migrated_0001.js
 class_method_kinds/polymorphic_getter.js
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-internal_slot/object_method.js
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 numbers/underscored_bin.js
 numbers/underscored_float.js
 numbers/underscored_float_whole.js