diff --git a/libraries/GCS_MAVLink/GCS.h b/libraries/GCS_MAVLink/GCS.h
index 5a9e873492..5cede26e55 100644
--- a/libraries/GCS_MAVLink/GCS.h
+++ b/libraries/GCS_MAVLink/GCS.h
@@ -50,6 +50,7 @@ enum ap_message {
     MSG_TERRAIN,
     MSG_BATTERY2,
     MSG_CAMERA_FEEDBACK,
+    MSG_MOUNT_STATUS,
     MSG_RETRY_DEFERRED // this must be last
 };