diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index fe24f8455617..9bc37154ec76 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_sysctl.c,v 1.185 2005/08/07 04:54:07 yamt Exp $	*/
+/*	$NetBSD: kern_sysctl.c,v 1.186 2005/08/21 13:14:54 yamt Exp $	*/
 
 /*-
  * Copyright (c) 2003 The NetBSD Foundation, Inc.
@@ -75,7 +75,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_sysctl.c,v 1.185 2005/08/07 04:54:07 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_sysctl.c,v 1.186 2005/08/21 13:14:54 yamt Exp $");
 
 #include "opt_defcorename.h"
 #include "opt_insecure.h"
@@ -2545,17 +2545,27 @@ old_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
 	   void *newp, size_t newlen, struct lwp *l)
 {
 	int error;
-	size_t savelen = *oldlenp;
+	size_t oldlen = 0;
+	size_t savelen;
+
+	if (oldlenp) {
+		oldlen = *oldlenp;
+	}
+	savelen = oldlen;
 
 	error = sysctl_lock(l, oldp, savelen);
 	if (error)
 		return (error);
-	error = sysctl_dispatch(name, namelen, oldp, oldlenp,
+	error = sysctl_dispatch(name, namelen, oldp, &oldlen,
 				newp, newlen, name, l, NULL);
 	sysctl_unlock(l);
-	if (error == 0 && oldp != NULL && savelen < *oldlenp)
+	if (error == 0 && oldp != NULL && savelen < oldlen)
 		error = ENOMEM;
 
+	if (oldlenp) {
+		*oldlenp = oldlen;
+	}
+
 	return (error);
 }