diff --git a/services/mattermost.nix b/services/mattermost.nix
index b70d234..f60302c 100644
--- a/services/mattermost.nix
+++ b/services/mattermost.nix
@@ -36,6 +36,9 @@ in {
 
       systemd.services.mattermost.serviceConfig.EnvironmentFile =
         "/persist/mattermost/secrets.env";
+      # overwrite the -c flag given in the module. this can be removed once we're on nixos 22.05
+      systemd.services.mattermost.serviceConfig.ExecStart =
+        lib.mkForce "${pkgs.mattermost}/bin/mattermost -c /persist/mattermost/config/config.json";
 
       # couldn't figure out how to actually overwrite modules, so now
       # there's two mattermost modules ...
@@ -125,7 +128,7 @@ in {
             EnableSMTPAuth = true;
             SMTPUsername = "noreply@infra4future.de";
             SMTPServer = "mail.hacc.space";
-            SMTPPort = 465;
+            SMTPPort = "465";
             SMTPServerTimeout = 10;
             ConnectionSecurity = "TLS";
           };