diff --git a/babel-preset/configs/hmr.js b/babel-preset/configs/hmr.js
index 9131810eb..d45d4369a 100644
--- a/babel-preset/configs/hmr.js
+++ b/babel-preset/configs/hmr.js
@@ -18,6 +18,12 @@ module.exports = function(options, filename) {
   var transform = filename
       ? './' + path.relative(path.dirname(filename), transformPath) // packager can't handle absolute paths
       : hmrTransform;
+
+  // Fix the module path to use '/' on Windows.
+  if (path.sep === '\\') {
+    transform = transform.replace(/\\/g, '/');
+  }
+
   return {
     plugins: resolvePlugins([
       [
diff --git a/packager/react-packager/src/Bundler/index.js b/packager/react-packager/src/Bundler/index.js
index 2fd484c0b..30da6417e 100644
--- a/packager/react-packager/src/Bundler/index.js
+++ b/packager/react-packager/src/Bundler/index.js
@@ -189,23 +189,24 @@ class Bundler {
     );
   }
 
-  _hmrURL(prefix, platform, extensionOverride, path) {
-    const matchingRoot = this._projectRoots.find(root => path.startsWith(root));
+  _hmrURL(prefix, platform, extensionOverride, filePath) {
+    const matchingRoot = this._projectRoots.find(root => filePath.startsWith(root));
 
     if (!matchingRoot) {
-      throw new Error('No matching project root for ', path);
+      throw new Error('No matching project root for ', filePath);
     }
 
-    const extensionStart = path.lastIndexOf('.');
-    let resource = path.substring(
+    // Replaces '\' with '/' for Windows paths.
+    if (path.sep === '\\') {
+      filePath = filePath.replace(/\\/g, '/');
+    }
+
+    const extensionStart = filePath.lastIndexOf('.');
+    let resource = filePath.substring(
       matchingRoot.length,
       extensionStart !== -1 ? extensionStart : undefined,
     );
 
-    const extension = extensionStart !== -1
-      ? path.substring(extensionStart + 1)
-      : null;
-
     return (
       prefix + resource +
       '.' + extensionOverride + '?' +