diff --git a/include/input/Input.h b/include/input/Input.h
index e281675..30b0d6a 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -550,6 +550,8 @@
     nsecs_t mEventTime;
 };
 
+std::ostream& operator<<(std::ostream& out, const KeyEvent& event);
+
 /*
  * Motion events.
  */