diff --git a/src/modules/mavlink/mavlink_receiver.cpp b/src/modules/mavlink/mavlink_receiver.cpp
index 7667506d9a..fb97e5ee1d 100644
--- a/src/modules/mavlink/mavlink_receiver.cpp
+++ b/src/modules/mavlink/mavlink_receiver.cpp
@@ -477,14 +477,18 @@ MavlinkReceiver::handle_message_command_int(mavlink_message_t *msg)
 		vcmd.frame = vehicle_command_s::FRAME_GLOBAL;
 		break;
 
+	case MAV_FRAME_GLOBAL_RELATIVE_ALT:
+
+	// FALLTHROUGH
 	case MAV_FRAME_GLOBAL_RELATIVE_ALT_INT:
 		vcmd.frame = vehicle_command_s::FRAME_GLOBAL_RELATIVE_ALT;
 		break;
 
 	default:
 		vcmd.frame = vehicle_command_s::FRAME_UNKNOWN;
-		PX4_WARN("invalid frame %" PRIu8 " for command %" PRIu16, cmd_mavlink.frame, cmd_mavlink.command);
-		break;
+		PX4_ERR("invalid frame %" PRIu8 " for command %" PRIu16, cmd_mavlink.frame, cmd_mavlink.command);
+		acknowledge(msg->sysid, msg->compid, cmd_mavlink.command, vehicle_command_ack_s::VEHICLE_CMD_RESULT_DENIED);
+		return;
 	}
 
 	if (cmd_mavlink.x == INT32_MAX && cmd_mavlink.y == INT32_MAX) {