diff --git a/magnum_cluster_api/tests/unit/test_helm.py b/magnum_cluster_api/tests/unit/test_helm.py
index bf9b72c0..e9fcfb8b 100644
--- a/magnum_cluster_api/tests/unit/test_helm.py
+++ b/magnum_cluster_api/tests/unit/test_helm.py
@@ -43,7 +43,7 @@ def test_helm_upgrade(mocker):
                 namespace,
                 release_name,
             ),
-            mocker.call().stdout.__str__(),
+            mocker.call(("().stdout.__str__", (), {})),
             mocker.call(
                 "helm",
                 "upgrade",