diff --git a/parametrize_from_file/schema.py b/parametrize_from_file/schema.py
index 629aa59..4b971c1 100644
--- a/parametrize_from_file/schema.py
+++ b/parametrize_from_file/schema.py
@@ -93,7 +93,10 @@ def rename(names=None, /, **kwarg_names):
 
     Any parameters not explicitly mentioned will be kept unchanged.
     """
-    names = (names or {}) | kwarg_names
+    names = {
+            **(names or {}),
+            **kwarg_names,
+    }
     return lambda params: {
             names.get(k, k): v
             for k, v in params.items()