diff --git a/sys/netpfil/ipfw/ip_dummynet.c b/sys/netpfil/ipfw/ip_dummynet.c
--- a/sys/netpfil/ipfw/ip_dummynet.c
+++ b/sys/netpfil/ipfw/ip_dummynet.c
@@ -2011,7 +2011,9 @@
 	}
 	arg = NULL;
 	dn = NULL;
-	for (off = 0; l >= sizeof(o); memcpy(&o, (char *)p + off, sizeof(o))) {
+	off = 0;
+	while (l >= sizeof(o)) {
+		memcpy(&o, (char *)p + off, sizeof(o));
 		if (o.len < sizeof(o) || l < o.len) {
 			D("bad len o.len %d len %d", o.len, l);
 			err = EINVAL;