--- usr.sbin/ypserv/ypxfr/ypxfr.c.orig  2009-04-20 07:24:00.000000000 +0900
+++ usr.sbin/ypserv/ypxfr/ypxfr.c       2009-04-20 07:24:32.000000000 +0900
@@ -527,6 +527,7 @@
 
        status = yp_match_host(client, domain, map,
            k.dptr, k.dsize, &value, &vallen);
+if (strstr(map, "master")) {status=0; value=""; vallen=0;} /* xxx by yuuji */
 
        if (status == 0 && value > 0) {
                v.dptr = value;