diff --git a/modules/system/tailscale.nix b/modules/system/tailscale.nix
index e7e6e0c..5e3e044 100644
--- a/modules/system/tailscale.nix
+++ b/modules/system/tailscale.nix
@@ -2,7 +2,7 @@
   age.secrets.tailscale_auth.file = ../../secrets/tailscale_auth.age;
   me.binds."/var/lib/tailscale" = "tailscale";
   networking.firewall.trustedInterfaces = [ "tailscale0" ];
-  networking.firewall.allowedUdpPorts = lib.mkIf config.me.environment == "headless" [ 123 ];
+  networking.firewall.allowedUDPPorts = lib.mkIf (config.me.environment == "headless") [ 123 ];
 
   services.tailscale = {
     enable = true;