--- linux-2.4.19-rsn1/net/ipv4/netfilter/ip_conntrack_proto_gre.c.orig	2002-09-08 00:29:55.000000000 +0200
+++ linux-2.4.19-rsn1/net/ipv4/netfilter/ip_conntrack_proto_gre.c	2002-09-08 00:20:45.000000000 +0200
@@ -230,6 +230,10 @@
 		      struct iphdr *iph, size_t len,
 		      enum ip_conntrack_info conntrackinfo)
 {
+	/* This is a reply packet, set conntrack to replied. */
+	if (CTINFO2DIR(conntrackinfo) == IP_CT_DIR_REPLY)
+		set_bit(IPS_SEEN_REPLY_BIT, &ct->status);
+
 	/* If we've seen traffic both ways, this is a GRE connection.
 	 * Extend timeout. */
 	if (ct->status & IPS_SEEN_REPLY) {