diff --git a/sys/arch/acorn32/mainbus/fd.c b/sys/arch/acorn32/mainbus/fd.c
index 42379dad0f08..ef7eaa85fdb2 100644
--- a/sys/arch/acorn32/mainbus/fd.c
+++ b/sys/arch/acorn32/mainbus/fd.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: fd.c,v 1.35 2008/01/02 11:48:20 ad Exp $	*/
+/*	$NetBSD: fd.c,v 1.36 2008/01/05 17:38:50 ad Exp $	*/
 
 /*-
  * Copyright (c) 1998 The NetBSD Foundation, Inc.
@@ -89,7 +89,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fd.c,v 1.35 2008/01/02 11:48:20 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fd.c,v 1.36 2008/01/05 17:38:50 ad Exp $");
 
 #include "opt_ddb.h"
 
@@ -1543,7 +1543,7 @@ fdformat(dev, finfo, l)
 	/* XXX very dodgy */
 	mutex_enter(bp->b_objlock);
 	while (!(bp->b_oflags & BO_DONE)) {
-		rv = cv_timedwait(&bp->b_done, 20 * hz);
+		rv = cv_timedwait(&bp->b_done, bp->b_objlock, 20 * hz);
 		if (rv == EWOULDBLOCK)
 			break;
 	}