diff --git a/src/modules/commander/px4_custom_mode.h b/src/modules/commander/px4_custom_mode.h
index b3e9de3aba..c65432f5e9 100644
--- a/src/modules/commander/px4_custom_mode.h
+++ b/src/modules/commander/px4_custom_mode.h
@@ -50,7 +50,8 @@ enum PX4_CUSTOM_MAIN_MODE {
 	PX4_CUSTOM_MAIN_MODE_ACRO,
 	PX4_CUSTOM_MAIN_MODE_OFFBOARD,
 	PX4_CUSTOM_MAIN_MODE_STABILIZED,
-	PX4_CUSTOM_MAIN_MODE_RATTITUDE
+	PX4_CUSTOM_MAIN_MODE_RATTITUDE,
+	PX4_CUSTOM_MAIN_MODE_SIMPLE /* unused, but reserved for future use */
 };
 
 enum PX4_CUSTOM_SUB_MODE_AUTO {