diff --git a/VERSION b/VERSION
index 3303dc1e62..f0937ee638 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-5.8.9
\ No newline at end of file
+5.8.12
\ No newline at end of file
diff --git a/packages/babel-cli/package.json b/packages/babel-cli/package.json
index ed7178ede4..69b3c8f2df 100644
--- a/packages/babel-cli/package.json
+++ b/packages/babel-cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "babel",
-  "version": "5.8.9",
+  "version": "5.8.12",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
diff --git a/packages/babel-runtime/package.json b/packages/babel-runtime/package.json
index dbece90bf8..52de34f260 100644
--- a/packages/babel-runtime/package.json
+++ b/packages/babel-runtime/package.json
@@ -1,6 +1,6 @@
 {
   "name": "babel-runtime",
-  "version": "5.8.9",
+  "version": "5.8.12",
   "description": "babel selfContained runtime",
   "license": "MIT",
   "repository": "babel/babel",
diff --git a/packages/babel/package.json b/packages/babel/package.json
index b4701628f6..58f9d78740 100644
--- a/packages/babel/package.json
+++ b/packages/babel/package.json
@@ -1,6 +1,6 @@
 {
   "name": "babel-core",
-  "version": "5.8.9",
+  "version": "5.8.12",
   "description": "A compiler for writing next generation JavaScript",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
@@ -42,7 +42,7 @@
     "babel-plugin-runtime": "^1.0.7",
     "babel-plugin-undeclared-variables-check": "^1.0.2",
     "babel-plugin-undefined-to-void": "^1.1.6",
-    "babylon": "^5.8.9",
+    "babylon": "^5.8.12",
     "bluebird": "^2.9.33",
     "chalk": "^1.0.0",
     "convert-source-map": "^1.1.0",
diff --git a/packages/babel/src/transformation/modules/_default.js b/packages/babel/src/transformation/modules/_default.js
index 48c9af8331..940e10e3ef 100644
--- a/packages/babel/src/transformation/modules/_default.js
+++ b/packages/babel/src/transformation/modules/_default.js
@@ -333,14 +333,14 @@ export default class DefaultFormatter {
   getModuleName() {
     var opts = this.file.opts;
     // moduleId is n/a if a `getModuleId()` is provided
-    if (opts.moduleId && !opts.getModuleId) {
+    if (opts.moduleId != null && !opts.getModuleId) {
       return opts.moduleId;
     }
 
     var filenameRelative = opts.filenameRelative;
     var moduleName = "";
 
-    if (opts.moduleRoot) {
+    if (opts.moduleRoot != null) {
       moduleName = opts.moduleRoot + "/";
     }
 
@@ -348,7 +348,7 @@ export default class DefaultFormatter {
       return moduleName + opts.filename.replace(/^\//, "");
     }
 
-    if (opts.sourceRoot) {
+    if (opts.sourceRoot != null) {
       // remove sourceRoot from filename
       var sourceRootRegEx = new RegExp("^" + opts.sourceRoot + "\/?");
       filenameRelative = filenameRelative.replace(sourceRootRegEx, "");
diff --git a/packages/babel/src/transformation/transformers/es6/parameters/rest.js b/packages/babel/src/transformation/transformers/es6/parameters/rest.js
index 963e070d17..5388a37a8e 100644
--- a/packages/babel/src/transformation/transformers/es6/parameters/rest.js
+++ b/packages/babel/src/transformation/transformers/es6/parameters/rest.js
@@ -78,6 +78,18 @@ var memberExpressionOptimisationVisitor = {
 
       state.references.push(this);
     }
+  },
+
+  /**
+   * Deopt on use of a binding identifier with the same name as our rest param.
+   *
+   * See https://github.com/babel/babel/issues/2091
+   */
+
+  BindingIdentifier(node, parent, scope, state) {
+    if (node.name === state.name) {
+      state.deopted = true;
+    }
   }
 };
 
diff --git a/packages/babel/src/types/retrievers.js b/packages/babel/src/types/retrievers.js
index fd8c4caf4f..8b5fcd9504 100644
--- a/packages/babel/src/types/retrievers.js
+++ b/packages/babel/src/types/retrievers.js
@@ -65,7 +65,6 @@ getBindingIdentifiers.keys = {
   ClassDeclaration: "id",
   ClassExpression: "id",
 
-  SpreadElement: "argument",
   RestElement: "argument",
   UpdateExpression: "argument",
 
diff --git a/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/actual.js b/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/actual.js
new file mode 100644
index 0000000000..43adbba736
--- /dev/null
+++ b/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/actual.js
@@ -0,0 +1 @@
+const deepAssign = (...args) => args = [];
diff --git a/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/expected.js b/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/expected.js
new file mode 100644
index 0000000000..b5288257f7
--- /dev/null
+++ b/packages/babel/test/fixtures/transformation/es6.parameters/rest-binding-deoptimisation/expected.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var deepAssign = function deepAssign() {
+  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
+    args[_key] = arguments[_key];
+  }
+
+  return args = [];
+};
diff --git a/packages/babylon/package.json b/packages/babylon/package.json
index 335a72163c..d46625f92a 100644
--- a/packages/babylon/package.json
+++ b/packages/babylon/package.json
@@ -1,6 +1,6 @@
 {
   "name": "babylon",
-  "version": "5.8.9",
+  "version": "5.8.12",
   "description": "",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",