diff --git a/sys/dev/usb/uaudio.c b/sys/dev/usb/uaudio.c
index 6dde82ce709d..309fefbdbfd8 100644
--- a/sys/dev/usb/uaudio.c
+++ b/sys/dev/usb/uaudio.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: uaudio.c,v 1.27 2000/06/19 11:43:48 augustss Exp $	*/
+/*	$NetBSD: uaudio.c,v 1.28 2000/08/24 14:11:09 augustss Exp $	*/
 
 /*
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -961,6 +961,9 @@ uaudio_add_extension(struct uaudio_softc *sc, usb_descriptor_t *v,
 	DPRINTFN(2,("uaudio_add_extension: bUnitId=%d bNrInPins=%d\n",
 		    d->bUnitId, d->bNrInPins));
 
+	if (usbd_get_quirks(sc->sc_udev)->uq_flags & UQ_NO_XU)
+		return;
+
 	if (d1->bmControls[0] & UA_EXT_ENABLE_MASK) {
 		mix.wIndex = MAKE(d->bUnitId, sc->sc_ac_iface);
 		mix.nchan = 1;
diff --git a/sys/dev/usb/usb_quirks.c b/sys/dev/usb/usb_quirks.c
index d629dd08c0b4..3002785dee5a 100644
--- a/sys/dev/usb/usb_quirks.c
+++ b/sys/dev/usb/usb_quirks.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: usb_quirks.c,v 1.27 2000/06/01 14:29:01 augustss Exp $	*/
+/*	$NetBSD: usb_quirks.c,v 1.28 2000/08/24 14:11:09 augustss Exp $	*/
 /*	$FreeBSD: src/sys/dev/usb/usb_quirks.c,v 1.13 1999/11/17 22:33:47 n_hibma Exp $	*/
 
 /*
@@ -64,9 +64,11 @@ Static struct usbd_quirk_entry {
  { USB_VENDOR_PERACOM, USB_PRODUCT_PERACOM_SERIAL1, 0x101, { UQ_NO_STRINGS }},
  { USB_VENDOR_WACOM, USB_PRODUCT_WACOM_CT0405U,     0x101, { UQ_NO_STRINGS }},
  { USB_VENDOR_DALLAS, USB_PRODUCT_DALLAS_J6502,	    0x0a2, { UQ_BAD_ADC }},
+ { USB_VENDOR_DALLAS, USB_PRODUCT_DALLAS_J6502,	    0x0a2, { UQ_NO_XU }},
  { USB_VENDOR_ALTEC, USB_PRODUCT_ALTEC_ADA70,	    0x103, { UQ_BAD_ADC }},
  { USB_VENDOR_ALTEC, USB_PRODUCT_ALTEC_ASC495,      0x000, { UQ_BAD_AUDIO }},
  { USB_VENDOR_QTRONIX, USB_PRODUCT_QTRONIX_980N,    0x110, { UQ_SPUR_BUT_UP }},
+ { USB_VENDOR_ALCOR2, USB_PRODUCT_ALCOR2_KBD_HUB,   0x001, { UQ_SPUR_BUT_UP }},
  { USB_VENDOR_MCT, USB_PRODUCT_MCT_HUB0100,         0x102, { UQ_BUS_POWERED }},
  { USB_VENDOR_MCT, USB_PRODUCT_MCT_USB232,          0x102, { UQ_BUS_POWERED }},
  { 0, 0, 0, { 0 } }
diff --git a/sys/dev/usb/usb_quirks.h b/sys/dev/usb/usb_quirks.h
index 31eeed49765a..e74cd05d6541 100644
--- a/sys/dev/usb/usb_quirks.h
+++ b/sys/dev/usb/usb_quirks.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: usb_quirks.h,v 1.12 2000/06/01 14:29:02 augustss Exp $	*/
+/*	$NetBSD: usb_quirks.h,v 1.13 2000/08/24 14:11:09 augustss Exp $	*/
 /*	$FreeBSD: src/sys/dev/usb/usb_quirks.h,v 1.9 1999/11/12 23:31:03 n_hibma Exp $	*/
 
 /*
@@ -40,14 +40,15 @@
 
 struct usbd_quirks {
 	u_int32_t uq_flags;	/* Device problems: */
-#define UQ_NO_SET_PROTO	0x01	/* cannot handle SET PROTOCOL. */
-#define UQ_SWAP_UNICODE	0x02	/* has some Unicode strings swapped. */
-#define UQ_MS_REVZ	0x04	/* mouse has Z-axis reversed */
-#define UQ_NO_STRINGS	0x08	/* string descriptors are broken. */
-#define UQ_BAD_ADC	0x10	/* bad audio spec version number. */
-#define UQ_BUS_POWERED	0x20	/* device is bus powered, despite claim */
-#define UQ_BAD_AUDIO	0x40	/* device claims audio class, but isn't */
-#define UQ_SPUR_BUT_UP	0x80	/* spurious mouse button up events */
+#define UQ_NO_SET_PROTO	0x0001	/* cannot handle SET PROTOCOL. */
+#define UQ_SWAP_UNICODE	0x0002	/* has some Unicode strings swapped. */
+#define UQ_MS_REVZ	0x0004	/* mouse has Z-axis reversed */
+#define UQ_NO_STRINGS	0x0008	/* string descriptors are broken. */
+#define UQ_BAD_ADC	0x0010	/* bad audio spec version number. */
+#define UQ_BUS_POWERED	0x0020	/* device is bus powered, despite claim */
+#define UQ_BAD_AUDIO	0x0040	/* device claims audio class, but isn't */
+#define UQ_SPUR_BUT_UP	0x0080	/* spurious mouse button up events */
+#define UQ_NO_XU	0x0100	/* audio device has broken extension unit */
 };
 
 extern struct usbd_quirks usbd_no_quirk;