diff --git a/weaviate/rbac/executor.py b/weaviate/rbac/executor.py
index bbaaebcfc..4729d7f88 100644
--- a/weaviate/rbac/executor.py
+++ b/weaviate/rbac/executor.py
@@ -33,7 +33,7 @@ def _flatten_permissions(
         if isinstance(permission, _Permission):
             flattened_permissions.append(permission)
         else:
-            flattened_permissions.extend(permission)
+            flattened_permissions += permission
     return flattened_permissions