diff --git a/packages/metro-bundler/src/Bundler/__tests__/Bundler-test.js b/packages/metro-bundler/src/Bundler/__tests__/Bundler-test.js
index b4becd75..dd13c5ea 100644
--- a/packages/metro-bundler/src/Bundler/__tests__/Bundler-test.js
+++ b/packages/metro-bundler/src/Bundler/__tests__/Bundler-test.js
@@ -270,14 +270,20 @@ describe('Bundler', function() {
       // jest calledWith does not support jasmine.any
       expect(getDependencies.mock.calls[0].slice(0, -2)).toEqual([
         '/root/foo.js',
-        {dev: true, recursive: true},
-        {minify: false,
+        {dev: true, platform: undefined, recursive: true},
+        {
           dev: true,
+          minify: false,
+          platform: undefined,
           transform: {
             dev: true,
-            hot: false,
             generateSourceMaps: false,
+            hot: false,
+            inlineRequires: false,
+            platform: undefined,
+            preloadedModules: undefined,
             projectRoots,
+            ramGroups: undefined,
           },
         },
       ])
diff --git a/packages/metro-bundler/src/Bundler/index.js b/packages/metro-bundler/src/Bundler/index.js
index 3bba3e84..eb0252eb 100644
--- a/packages/metro-bundler/src/Bundler/index.js
+++ b/packages/metro-bundler/src/Bundler/index.js
@@ -751,22 +751,31 @@ class Bundler {
 
   getTransformOptions(
     mainModuleName: string,
-    options: {
-      dev?: boolean,
-      generateSourceMaps?: boolean,
-      hot?: boolean,
+    options: {|
+      dev: boolean,
+      generateSourceMaps: boolean,
+      hot: boolean,
       platform: string,
       projectRoots: Array<string>,
-    },
+    |},
   ): Promise<TransformOptions> {
     const getDependencies = (entryFile: string) =>
       this.getDependencies({...options, entryFile})
         .then(r => r.dependencies.map(d => d.path));
 
-    const extraOptions: Promise<?ExtraTransformOptions> = this._getTransformOptions
+    const extraOptions: Promise<ExtraTransformOptions> = this._getTransformOptions
       ? this._getTransformOptions(mainModuleName, options, getDependencies)
-      : Promise.resolve(null);
-    return extraOptions.then(extraOpts => ({...options, ...extraOpts}));
+      : Promise.resolve({});
+    return extraOptions.then(extraOpts => ({
+      dev: options.dev,
+      generateSourceMaps: options.generateSourceMaps,
+      hot: options.hot,
+      inlineRequires: extraOpts.inlineRequires || false,
+      platform: options.platform,
+      preloadedModules: extraOpts.preloadedModules,
+      projectRoots: options.projectRoots,
+      ramGroups: extraOpts.ramGroups,
+    }));
   }
 
   getResolver(): Promise<Resolver> {
diff --git a/packages/metro-bundler/src/JSTransformer/worker/worker.js b/packages/metro-bundler/src/JSTransformer/worker/worker.js
index e29099e0..0e075651 100644
--- a/packages/metro-bundler/src/JSTransformer/worker/worker.js
+++ b/packages/metro-bundler/src/JSTransformer/worker/worker.js
@@ -18,7 +18,7 @@ const invariant = require('fbjs/lib/invariant');
 const minify = require('./minify');
 
 import type {LogEntry} from '../../Logger/Types';
-import type {Ast, SourceMap, TransformOptions as BabelTransformOptions} from 'babel-core';
+import type {Ast, SourceMap} from 'babel-core';
 
 export type TransformedCode = {
   code: string,
@@ -35,23 +35,23 @@ type Transformer = {
   ) => {ast: ?Ast, code: string, map: ?SourceMap}
 };
 
-export type TransformOptions = {
+export type TransformOptions = {|
   +dev: boolean,
   +generateSourceMaps: boolean,
   +hot: boolean,
   +inlineRequires: {+blacklist: {[string]: true}} | boolean,
   +platform: string,
-  +preloadedModules?: Array<string> | false,
+  +preloadedModules: ?Array<string> | false,
   +projectRoots: Array<string>,
-  +ramGroups?: Array<string>,
-} & BabelTransformOptions;
+  +ramGroups: ?Array<string>,
+|};
 
-export type Options = {
+export type Options = {|
   +dev: boolean,
   +minify: boolean,
   +platform: string,
   +transform: TransformOptions,
-};
+|};
 
 export type Data = {
   result: TransformedCode,
diff --git a/packages/metro-bundler/src/lib/ModuleTransport.js b/packages/metro-bundler/src/lib/ModuleTransport.js
index 14133660..6f2fd801 100644
--- a/packages/metro-bundler/src/lib/ModuleTransport.js
+++ b/packages/metro-bundler/src/lib/ModuleTransport.js
@@ -19,7 +19,7 @@ type SourceMapOrMappings = MixedSourceMap | Array<RawMapping>;
 type Metadata = {
   dependencies?: ?Array<string>,
   dependencyPairs?: Array<[mixed, {path: string}]>,
-  preloaded?: boolean,
+  preloaded: ?boolean,
 };
 
 class ModuleTransport {