diff --git a/react-packager/src/DependencyResolver/polyfills/prelude.js b/react-packager/src/DependencyResolver/polyfills/prelude.js
index 9f4db44e..a1004b7d 100644
--- a/react-packager/src/DependencyResolver/polyfills/prelude.js
+++ b/react-packager/src/DependencyResolver/polyfills/prelude.js
@@ -1,2 +1,5 @@
 /* eslint global-strict:0 */
 __DEV__ = false;
+
+/* global __BUNDLE_START_TIME__:true */
+__BUNDLE_START_TIME__ = Date.now();
diff --git a/react-packager/src/DependencyResolver/polyfills/prelude_dev.js b/react-packager/src/DependencyResolver/polyfills/prelude_dev.js
index 26b26a07..14b97faa 100644
--- a/react-packager/src/DependencyResolver/polyfills/prelude_dev.js
+++ b/react-packager/src/DependencyResolver/polyfills/prelude_dev.js
@@ -1,2 +1,5 @@
 /* eslint global-strict:0 */
 __DEV__ = true;
+
+/* global __BUNDLE_START_TIME__:true */
+__BUNDLE_START_TIME__ = Date.now();