diff --git a/docs/topics/db/models.txt b/docs/topics/db/models.txt
index 244e9bbb16..ee4bdab7bb 100644
--- a/docs/topics/db/models.txt
+++ b/docs/topics/db/models.txt
@@ -918,7 +918,7 @@ example::
             if (
                 update_fields := kwargs.get("update_fields")
             ) is not None and "name" in update_fields:
-                update_fields = {"slug"}.union(update_fields)
+                kwargs["update_fields"] = {"slug"}.union(update_fields)
             super().save(**kwargs)
 
 See :ref:`ref-models-update-fields` for more details.