diff --git a/flow-typed/babel.js.flow b/flow-typed/babel.js.flow
index ddfcf8ae..5893a444 100644
--- a/flow-typed/babel.js.flow
+++ b/flow-typed/babel.js.flow
@@ -89,7 +89,9 @@ type __TransformOptions = {
 
 type _TransformOptions =
   __TransformOptions & {env?: {[key: string]: __TransformOptions}};
-declare class Ast {}
+
+type Ast = {};
+
 type TransformResult = {
   ast: Ast,
   code: ?string,
@@ -101,7 +103,7 @@ type VisitFn = <State>(path: Object, state: State) => any;
 declare module 'babel-core' {
   declare type Plugins = _Plugins;
   declare type SourceMap = _SourceMap;
-  declare type Ast = Ast;
+  declare type Ast = {};
   declare type TransformOptions = _TransformOptions;
   declare function transform(
     code: string,
diff --git a/packages/metro/src/JSTransformer/worker/index.js b/packages/metro/src/JSTransformer/worker/index.js
index b8843bb1..135da666 100644
--- a/packages/metro/src/JSTransformer/worker/index.js
+++ b/packages/metro/src/JSTransformer/worker/index.js
@@ -47,7 +47,7 @@ export type TransformArgs<ExtraOptions: {}> = {|
 |};
 
 export type TransformResults = {
-  ast: ?Ast,
+  ast: Ast,
 };
 
 export type Transform<ExtraOptions: {}> = (
diff --git a/packages/metro/src/assetTransformer.js b/packages/metro/src/assetTransformer.js
index de34c76a..f4817ca1 100644
--- a/packages/metro/src/assetTransformer.js
+++ b/packages/metro/src/assetTransformer.js
@@ -15,6 +15,7 @@ const {getAssetData} = require('./Assets');
 const {generateAssetCodeFileAst} = require('./Bundler/util');
 
 import type {TransformOptions} from './JSTransformer/worker';
+import type {Ast} from 'babel-core';
 
 type Params = {
   localPath: string,