diff --git a/include/rtdef.h b/include/rtdef.h
index 6498d217fd..5cb6e6359e 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -532,6 +532,7 @@ enum rt_device_class_type
 	RT_Device_Class_MTD,		/* memory device */
 	RT_Device_Class_CAN,		/* CAN device */
 	RT_Device_Class_RTC,		/* RTC device */
+	RT_Device_Class_Sound,		/* Sound device */
 	RT_Device_Class_Unknown		/* unknown device */
 };