diff --git a/init.d/sysv/custom.d.examples/10-keenetic-udp-fix b/init.d/sysv/custom.d.examples/10-keenetic-udp-fix
index e04706c..554e6fb 100644
--- a/init.d/sysv/custom.d.examples/10-keenetic-udp-fix
+++ b/init.d/sysv/custom.d.examples/10-keenetic-udp-fix
@@ -8,12 +8,13 @@ zapret_custom_firewall()
 {
 	# $1 - 1 - add, 0 - stop
 
-	local wan wanif
+	local wan wanif rule
 
 	# use IFACE_WAN if defined. if not - search for interfaces with default route.
 	wanif=${IFACE_WAN:-$(sed -nre 's/^([^\t]+)\t00000000\t[0-9A-F]{8}\t[0-9A-F]{4}\t[0-9]+\t[0-9]+\t[0-9]+\t00000000.*$/\1/p' /proc/net/route | sort -u | xargs)}
 	for wan in $wanif; do
-		ipt_print_op $1 "-o $wan -j MASQUERADE" "keenetic udp fix"
-		ipt_add_del $1 POSTROUTING -t nat -o $wan -j MASQUERADE
+		rule="-o $wan -p udp -m mark --mark $DESYNC_MARK/$DESYNC_MARK"
+		ipt_print_op $1 "$rule" "keenetic udp fix"
+		ipt_add_del $1 POSTROUTING -t nat $rule -j MASQUERADE
 	done
 }