diff --git a/nixos/modules/services/web-apps/anuko-time-tracker.nix b/nixos/modules/services/web-apps/anuko-time-tracker.nix
index 52cbfd5ae4f0..4d00d418a1dc 100644
--- a/nixos/modules/services/web-apps/anuko-time-tracker.nix
+++ b/nixos/modules/services/web-apps/anuko-time-tracker.nix
@@ -225,7 +225,7 @@ in
         };
 
         smtpPort = lib.mkOption {
-          type = lib.types.int;
+          type = lib.types.port;
           description = "MTA port.";
           default = 25;
         };