diff --git a/packages/babel-generator/src/generators/flow.js b/packages/babel-generator/src/generators/flow.js
index 86088bdd40..75a1147535 100644
--- a/packages/babel-generator/src/generators/flow.js
+++ b/packages/babel-generator/src/generators/flow.js
@@ -198,8 +198,10 @@ export function FunctionTypeAnnotation(node: Object, parent: Object) {
 export function FunctionTypeParam(node: Object) {
   this.print(node.name, node);
   if (node.optional) this.token("?");
-  this.token(":");
-  this.space();
+  if (node.name) {
+    this.token(":");
+    this.space();
+  }
   this.print(node.typeAnnotation, node);
 }
 
diff --git a/packages/babel-generator/test/fixtures/flow/type-alias/input.js b/packages/babel-generator/test/fixtures/flow/type-alias/input.js
index f53e79be1e..ed16c5d28d 100644
--- a/packages/babel-generator/test/fixtures/flow/type-alias/input.js
+++ b/packages/babel-generator/test/fixtures/flow/type-alias/input.js
@@ -12,3 +12,5 @@ type overloads =
   & ((x: string) => number)
   & ((x: number) => string)
 ;
+
+type func = string => string;
diff --git a/packages/babel-generator/test/fixtures/flow/type-alias/output.js b/packages/babel-generator/test/fixtures/flow/type-alias/output.js
index aeaaa87da9..dc12829d21 100644
--- a/packages/babel-generator/test/fixtures/flow/type-alias/output.js
+++ b/packages/babel-generator/test/fixtures/flow/type-alias/output.js
@@ -7,4 +7,5 @@ type union = {
 } | {
   type: "B"
 };
-type overloads = (x: string) => number & (x: number) => string;
\ No newline at end of file
+type overloads = (x: string) => number & (x: number) => string;
+type func = (string) => string;