diff --git a/web/system.py b/web/system.py
index 3dbc0b7..9639505 100644
--- a/web/system.py
+++ b/web/system.py
@@ -164,7 +164,7 @@ def save_config():
             # Print wireguard config.
             with open(output / 'etc/wireguard/wg.conf', 'w', encoding='utf-8') as f:
                 # Server configuration.
-                wg_intf = '[Interface]\nListenPort = {port}\nPrivateKey = {key}\n\n'
+                wg_intf = '[Interface]\nListenPort = {port}\nPrivateKey = {key}\nFwMark = 51820\n\n'
                 f.write(wg_intf.format(port=settings.get('wg_port') or 51820, key=settings.get('wg_key')))
 
                 # Client configuration.