diff --git a/atusb/fw/usb/dfu.c b/atusb/fw/usb/dfu.c
index 6efd9fd..a70c52b 100644
--- a/atusb/fw/usb/dfu.c
+++ b/atusb/fw/usb/dfu.c
@@ -77,15 +77,7 @@ const uint8_t config_descriptor[] = {
 
 	/* Interface #0 */
 
-	9,			/* bLength */
-	USB_DT_INTERFACE,	/* bDescriptorType */
-	0,			/* bInterfaceNumber */
-	0,			/* bAlternateSetting */
-	0,			/* bNumEndpoints */
-	0xfe,			/* bInterfaceClass (application specific) */
-	0x01,			/* bInterfaceSubClass (device fw upgrade) */
-	0x02,			/* bInterfaceProtocol (DFU mode protocol) */
-	0,			/* iInterface */
+	DFU_ITF_DESCR(0)
 };
 
 
diff --git a/atusb/fw/usb/dfu.h b/atusb/fw/usb/dfu.h
index 152e297..0f2d262 100644
--- a/atusb/fw/usb/dfu.h
+++ b/atusb/fw/usb/dfu.h
@@ -78,6 +78,18 @@ struct dfu {
 };
 
 
+#define	DFU_ITF_DESCR(itf)						     \
+	9,			/* bLength */				     \
+	USB_DT_INTERFACE,	/* bDescriptorType */			     \
+	(itf),			/* bInterfaceNumber */			     \
+	0,			/* bAlternateSetting */			     \
+	0,			/* bNumEndpoints */			     \
+	0xfe,			/* bInterfaceClass (application specific) */ \
+	0x01,			/* bInterfaceSubClass (device fw upgrade) */ \
+	0x02,			/* bInterfaceProtocol (DFU mode protocol) */ \
+	0,			/* iInterface */
+
+
 extern struct dfu dfu;