diff --git a/README.md b/README.md
index d078198..f4472d2 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,7 @@ FCM is just a demo of Android Application which implement Firebase Cloud Messagi
 * Supported Android 2.3 (Gingerbread) and newer
 * Google Play services 9.2.1 or newer
 * Android Studio 1.5 or higher
+* google-services.json in app-level folder
 
 ## Features
 * Subscribe and Unsubscribe with topics