diff --git a/sound/usb/card.h b/sound/usb/card.h
index bf2889a..5ecacaa 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -21,6 +21,7 @@
 	unsigned char endpoint;		/* endpoint */
 	unsigned char ep_attr;		/* endpoint attributes */
 	unsigned char datainterval;	/* log_2 of data packet interval */
+	unsigned char protocol;		/* UAC_VERSION_1/2 */
 	unsigned int maxpacksize;	/* max. packet size */
 	unsigned int rates;		/* rate bitmasks */
 	unsigned int rate_min, rate_max;	/* min/max rates */