diff --git a/instances/heimdall/configuration.nix b/instances/heimdall/configuration.nix
index 2ded5c4..0ebb681 100644
--- a/instances/heimdall/configuration.nix
+++ b/instances/heimdall/configuration.nix
@@ -87,6 +87,7 @@ in
       listeners = [{
         address = "127.0.0.1";
         port = 1883;
+        omitPasswordAuth = true;
         users.iotdevice = {
           acl = [
             "pattern readwrite #"