diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index f8903c1e10109a734a99172f696c233ad37867cf..9accde339601e6d736a281793ccf19d805a10df7 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -515,8 +515,8 @@ static int vlan_ioctl_handler(struct net *net, void __user *arg)
 		return -EFAULT;
 
 	/* Null terminate this sucker, just in case. */
-	args.device1[23] = 0;
-	args.u.device2[23] = 0;
+	args.device1[sizeof(args.device1) - 1] = 0;
+	args.u.device2[sizeof(args.u.device2) - 1] = 0;
 
 	rtnl_lock();