diff --git a/flake.nix b/flake.nix
index 2f8dfe6..6c84287 100644
--- a/flake.nix
+++ b/flake.nix
@@ -86,7 +86,7 @@
             wantedBy = [ "network.target" ];
             serviceConfig = {
               ExecStart = ''
-                ${cfg.package}/bin/tatoeba --port ${cfg.port}
+                ${cfg.package}/bin/tatoeba --port ${builtins.toString cfg.port}
               '';
               Restart = "always";
               DynamicUser = true;