diff --git a/usr.sbin/ndp/ndp.c b/usr.sbin/ndp/ndp.c
index a761f96260b4..256809afa14e 100644
--- a/usr.sbin/ndp/ndp.c
+++ b/usr.sbin/ndp/ndp.c
@@ -890,7 +890,7 @@ rtmsg(cmd)
 		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
 		if (rtm->rtm_flags & RTF_ANNOUNCE) {
 			rtm->rtm_flags &= ~RTF_HOST;
-			rtm->rtm_flags |= RTA_NETMASK;
+			rtm->rtm_addrs |= RTA_NETMASK;
 		}
 		/* FALLTHROUGH */
 	case RTM_GET: