diff --git a/lemmy-container.nix b/lemmy-container.nix
index 3f6d9e5..5cb5a10 100644
--- a/lemmy-container.nix
+++ b/lemmy-container.nix
@@ -98,7 +98,7 @@ in {
             server.package = cfg.server-package;
             settings = {
               email = {
-                smtp_server = "${cfg.smtp.host}:${cfg.smtp.port}";
+                smtp_server = "${cfg.smtp.host}:${toString cfg.smtp.port}";
                 smtp_from_address = "noreply@${cfg.hostname}";
               };
               hostname = cfg.hostname;