diff --git a/sys/net/ipfw3_layer2/ip_fw3_layer2.c b/sys/net/ipfw3_layer2/ip_fw3_layer2.c
--- a/sys/net/ipfw3_layer2/ip_fw3_layer2.c
+++ b/sys/net/ipfw3_layer2/ip_fw3_layer2.c
@@ -124,7 +124,8 @@
         if ((*args)->eh != NULL) {
                 struct sockaddr sa;
                 sa.sa_len = 8;
-                strncpy(sa.sa_data, (*args)->eh->ether_shost, 6);
+                memcpy(sa.sa_data, (*args)->eh->ether_shost, 6);
+                bzero(sa.sa_data + 6, sizeof(sa.sa_data) - 6);
                 ent = (struct table_mac_entry *)rnh->rnh_lookup(&sa, NULL, rnh);
                 if (ent != NULL)
                         *cmd_val = IP_FW_MATCH;