diff --git a/sys/netinet/libalias/alias_db.h b/sys/netinet/libalias/alias_db.h
index 971ca305c1a..26f055b2987 100644
--- a/sys/netinet/libalias/alias_db.h
+++ b/sys/netinet/libalias/alias_db.h
@@ -273,6 +273,7 @@ struct alias_link {
 #define LINK_FRAGMENT_PTR             (IPPROTO_MAX + 2)
 #define LINK_ADDR                     (IPPROTO_MAX + 3)
 #define LINK_PPTP                     (IPPROTO_MAX + 4)
+#define LINK_SYNC_MASK		      0x80000000
 
 	int		flags;	/* indicates special characteristics */
 	int		pflags;	/* protocol-specific flags */