diff --git a/flake.nix b/flake.nix
index 816d9ef..d748129 100644
--- a/flake.nix
+++ b/flake.nix
@@ -68,6 +68,13 @@
               The tatoeba package that should be used.
             '';
           };
+          port = lib.mkOption {
+            type = lib.types.port;
+            default = 3001;
+            description = lib.mdDoc ''
+              The port at which to run.
+            '';
+          };
         };
         config = {
           systemd.services.tatoeba = let
@@ -79,7 +86,7 @@
             wantedBy = [ "network.target" ];
             serviceConfig = {
               ExecStart = ''
-                ${cfg.package}/bin/tatoeba
+                ${cfg.package}/bin/tatoeba --port ${cfg.port}
               '';
               Restart = "always";
               DynamicUser = true;