diff --git a/headers/os/app/Invoker.h b/headers/os/app/Invoker.h
index 96b5cd2604..ee62279982 100644
--- a/headers/os/app/Invoker.h
+++ b/headers/os/app/Invoker.h
@@ -113,7 +113,7 @@ private:
 			BHandler	*fReplyTo;
 			bigtime_t	fTimeout;
 			uint32		fNotifyKind;
-			uint32		_reserved[2];	// to be able to keep binary compatibility
+			uint32		_reserved[1];	// to be able to keep binary compatibility
 };
 //------------------------------------------------------------------------------