diff --git a/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/input.ts b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/input.ts
new file mode 100644
index 0000000000..06818eda99
--- /dev/null
+++ b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/input.ts
@@ -0,0 +1 @@
+let x: (number) => void;
diff --git a/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/options.json b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/options.json
new file mode 100644
index 0000000000..05760686b4
--- /dev/null
+++ b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["syntax-typescript", "./plugin"]
+}
diff --git a/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/output.js b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/output.js
new file mode 100644
index 0000000000..a3d4a2a515
--- /dev/null
+++ b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/output.js
@@ -0,0 +1 @@
+let x: (string) => void;
diff --git a/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/plugin.js b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/plugin.js
new file mode 100644
index 0000000000..b2294ab701
--- /dev/null
+++ b/packages/babel-traverse/test/fixtures/regression/visit-tsfunctiontype-parameters/plugin.js
@@ -0,0 +1,11 @@
+module.exports = function() {
+  return {
+    visitor: {
+      Identifier(path) {
+        if (path.node.name == "number") {
+          path.node.name = "string";
+        }
+      }
+    }
+  };
+}
diff --git a/packages/babel-types/src/definitions/typescript.js b/packages/babel-types/src/definitions/typescript.js
index 4f321adb3b..f6a89fa8dc 100644
--- a/packages/babel-types/src/definitions/typescript.js
+++ b/packages/babel-types/src/definitions/typescript.js
@@ -156,7 +156,7 @@ defineType("TSThisType", {
 
 const fnOrCtr = {
   aliases: ["TSType"],
-  visitor: ["typeParameters", "typeAnnotation"],
+  visitor: ["typeParameters", "parameters", "typeAnnotation"],
   fields: signatureDeclarationCommon,
 };