diff --git a/mastodon-container.nix b/mastodon-container.nix
index 14d02bd..667e694 100644
--- a/mastodon-container.nix
+++ b/mastodon-container.nix
@@ -117,7 +117,7 @@ in {
       recommendedProxySettings = true;
       virtualHosts."${cfg.hostname}" = {
         locations."/" = {
-          proxyPass = "http://localhost:${cfg.port}";
+          proxyPass = "http://localhost:${toString cfg.port}";
           proxyWebsockets = true;
         };
       };