diff --git a/src/config.js b/src/config.js
index 28c9fc5a..2523f896 100644
--- a/src/config.js
+++ b/src/config.js
@@ -18,7 +18,8 @@ module.exports.WG_ALLOWED_IPS = process.env.WG_ALLOWED_IPS || '0.0.0.0/0, ::/0';
 
 module.exports.WG_PRE_UP = process.env.WG_PRE_UP || '';
 module.exports.WG_POST_UP = process.env.WG_POST_UP || `
-iptables -t nat -A POSTROUTING -s ${module.exports.WG_DEFAULT_ADDRESS.replace('x', '0')}/24 -o eth0 -j MASQUERADE;
+iptables -t mangle -A PREROUTING -i wg0 -j MARK --set-mark 0x30;
+iptables -t nat -A POSTROUTING ! -o wg0 -m mark --mark 0x30 -j MASQUERADE;
 iptables -A INPUT -p udp -m udp --dport 51820 -j ACCEPT;
 iptables -A FORWARD -i wg0 -j ACCEPT;
 iptables -A FORWARD -o wg0 -j ACCEPT;