diff --git a/local-cli/bundle/bundleCommandLineArgs.js b/local-cli/bundle/bundleCommandLineArgs.js
index 546829867d..77033b11a1 100644
--- a/local-cli/bundle/bundleCommandLineArgs.js
+++ b/local-cli/bundle/bundleCommandLineArgs.js
@@ -18,7 +18,6 @@ module.exports = [
     command: 'platform',
     description: 'Either "ios" or "android"',
     type: 'string',
-    required: true,
   }, {
     command: 'transformer',
     description: 'Specify a custom transformer to be used (absolute path)',
diff --git a/packager/react-packager/src/Server/index.js b/packager/react-packager/src/Server/index.js
index c18fe04afc..2b589d528b 100644
--- a/packager/react-packager/src/Server/index.js
+++ b/packager/react-packager/src/Server/index.js
@@ -11,6 +11,7 @@
 const Activity = require('../Activity');
 const AssetServer = require('../AssetServer');
 const FileWatcher = require('../FileWatcher');
+const getPlatformExtension = require('../lib/getPlatformExtension');
 const Bundler = require('../Bundler');
 const Promise = require('promise');
 
@@ -173,6 +174,10 @@ class Server {
 
   buildBundle(options) {
     return Promise.resolve().then(() => {
+      if (!options.platform) {
+        options.platform = getPlatformExtension(options.entryFile);
+      }
+
       const opts = bundleOpts(options);
       return this._bundler.bundle(
         opts.entryFile,
@@ -191,6 +196,10 @@ class Server {
 
   getDependencies(options) {
     return Promise.resolve().then(() => {
+      if (!options.platform) {
+        options.platform = getPlatformExtension(options.entryFile);
+      }
+
       const opts = dependencyOpts(options);
       return this._bundler.getDependencies(
         opts.entryFile,
@@ -432,6 +441,10 @@ class Server {
     const sourceMapUrlObj = _.clone(urlObj);
     sourceMapUrlObj.pathname = pathname.replace(/\.bundle$/, '.map');
 
+    // try to get the platform from the url
+    const platform = urlObj.query.platform ||
+      getPlatformExtension(pathname);
+
     return {
       sourceMapUrl: url.format(sourceMapUrlObj),
       entryFile: entryFile,
@@ -443,7 +456,7 @@ class Server {
         'inlineSourceMap',
         false
       ),
-      platform: urlObj.query.platform,
+      platform: platform,
     };
   }