diff --git a/sys/netinet/libalias/alias.c b/sys/netinet/libalias/alias.c
--- a/sys/netinet/libalias/alias.c
+++ b/sys/netinet/libalias/alias.c
@@ -912,6 +912,9 @@
 		/* Walk out chain. */
 		error = find_handler(OUT, UDP, la, pip, &ad);
 
+		if (error < 0)
+			return (PKT_ALIAS_IGNORED);
+
 		/* If UDP checksum is not zero, adjust since source port is */
 		/* being aliased and source address is being altered	*/
 		if (ud->uh_sum != 0) {
@@ -981,6 +984,9 @@
 		/* Walk out chain. */
 		error = find_handler(IN, TCP, la, pip, &ad);
 
+		if (error < 0)
+			return (PKT_ALIAS_IGNORED);
+
 		alias_address = GetAliasAddress(lnk);
 		original_address = GetOriginalAddress(lnk);
 		proxy_address = GetProxyAddress(lnk);
@@ -1150,6 +1156,9 @@
 		/* Walk out chain. */
 		error = find_handler(OUT, TCP, la, pip, &ad);
 
+		if (error < 0)
+			return (PKT_ALIAS_IGNORED);
+
 		/* Adjust TCP checksum since source port is being aliased
 		 * and source address is being altered */
 		accumulate = tc->th_sport;