--- sys/net/flowtable.c
+++ sys/net/flowtable.c
@@ -199,8 +199,8 @@
 	ip = mtod(m, struct ip *);
 
 	if (ip->ip_src.s_addr == ip->ip_dst.s_addr ||
-	    (ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET)
+	    IN_LOOPBACK(ntohl(ip->ip_dst.s_addr)) ||
+	    IN_LOOPBACK(ntohl(ip->ip_src.s_addr)))
 		return (NULL);
 
 	fibnum = M_GETFIB(m);