diff --git a/cmd/tailscaled/tailscaled.service b/cmd/tailscaled/tailscaled.service
index 2945a4e64..d5a65a42e 100644
--- a/cmd/tailscaled/tailscaled.service
+++ b/cmd/tailscaled/tailscaled.service
@@ -7,7 +7,7 @@ After=network-pre.target NetworkManager.service systemd-resolved.service
 [Service]
 EnvironmentFile=/etc/default/tailscaled
 ExecStartPre=/usr/sbin/tailscaled --cleanup
-ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --socket=/run/tailscale/tailscaled.sock --port $PORT $FLAGS
+ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --socket=/run/tailscale/tailscaled.sock --port=${PORT} $FLAGS
 ExecStopPost=/usr/sbin/tailscaled --cleanup
 
 Restart=on-failure