cd /usr/src/sys/nfs

and apply the following trivial patch.

--- nfs_subs.c~	Sat Apr  2 03:00:16 2005
+++ nfs_subs.c	Sat Jul  2 23:53:43 2005
@@ -1657,7 +1657,7 @@
 		return (error);
 
 	saddr = mtod(nam, struct sockaddr_in *);
-	if (saddr->sin_family == AF_INET &&
+	if (0 && saddr->sin_family == AF_INET &&
 	    (ntohs(saddr->sin_port) >= IPPORT_RESERVED ||
 	    (slp->ns_so->so_type == SOCK_STREAM && ntohs(saddr->sin_port) == 20))) {
 		vput(*vpp);