--- a/Assets/GoogleVR/Scripts/Keyboard/GvrKeyboard.cs
+++ b/Assets/GoogleVR/Scripts/Keyboard/GvrKeyboard.cs
@@ -313,6 +315,9 @@ public class GvrKeyboard : MonoBehaviour {
     }
   }

+  private delegate void KeyboardCallbackDelegate(IntPtr closure, GvrKeyboardEvent keyboardEvent);
+
+  [AOT.MonoPInvokeCallback(typeof(KeyboardCallbackDelegate))]
   private static void OnKeyboardCallback(IntPtr closure, GvrKeyboardEvent keyboardEvent) {
     lock (callbacksLock) {
       threadSafeCallbacks.Add(keyboardEvent);