diff -up ntp-4.2.6p5/ntpd/ntp_proto.c.orig ntp-4.2.6p5/ntpd/ntp_proto.c
--- ntp-4.2.6p5/ntpd/ntp_proto.c.orig	2015-11-06 10:48:42.672684827 +0100
+++ ntp-4.2.6p5/ntpd/ntp_proto.c	2015-11-06 13:03:14.284092484 +0100
@@ -1069,7 +1069,7 @@ receive(
 	 * the packet is not bogus in symmetric interleaved mode.
 	 */
 	} else if (peer->flip == 0) {
-		if (!L_ISEQU(&p_org, &peer->aorg)) {
+		if (L_ISZERO(&p_org) || !L_ISEQU(&p_org, &peer->aorg)) {
 			peer->bogusorg++;
 			peer->flash |= TEST2;	/* bogus */
 			if (!L_ISZERO(&peer->dst) && L_ISEQU(&p_org,