diff --git a/webmin-systemd b/webmin-systemd
index 91581682d..7edb1b55a 100644
--- a/webmin-systemd
+++ b/webmin-systemd
@@ -11,7 +11,7 @@ Type=forking
 Restart=always
 RestartSec=2s
 TimeoutSec=15s
-TimeoutStopSec=300
+TimeoutStopSec=300s
 
 [Install]
 WantedBy=multi-user.target