diff --git a/sys/dev/usb/if_urtwn.c b/sys/dev/usb/if_urtwn.c
index c5b794545f62..5fe1b3831ad3 100644
--- a/sys/dev/usb/if_urtwn.c
+++ b/sys/dev/usb/if_urtwn.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: if_urtwn.c,v 1.86 2020/04/16 17:18:27 nat Exp $	*/
+/*	$NetBSD: if_urtwn.c,v 1.87 2020/05/02 00:50:07 mrg Exp $	*/
 /*	$OpenBSD: if_urtwn.c,v 1.42 2015/02/10 23:25:46 mpi Exp $	*/
 
 /*-
@@ -25,7 +25,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_urtwn.c,v 1.86 2020/04/16 17:18:27 nat Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_urtwn.c,v 1.87 2020/05/02 00:50:07 mrg Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -584,6 +584,8 @@ urtwn_detach(device_t self, int flags)
 		ieee80211_ifdetach(&sc->sc_ic);
 		if_detach(ifp);
 
+		mutex_destroy(&sc->sc_media_mtx);
+
 		/* Close Tx/Rx pipes.  Abort done by urtwn_stop. */
 		urtwn_close_pipes(sc);
 	}