--- tcpmssd.c~	Mon Jul 17 20:57:24 2000
+++ tcpmssd.c	Mon Nov 13 10:10:37 2000
@@ -176,7 +176,7 @@
 			continue;
 		}
 
-		if (FD_ISSET(rtsock, &fdset)) {
+		if (rtsock != -1 && FD_ISSET(rtsock, &fdset)) {
 			struct if_msghdr ifm;
 
 			if ((pktlen = read(rtsock, &ifm, sizeof(ifm))) == -1) {