diff --git a/src/QueryBuilder/AbstractDMLQueryBuilder.php b/src/QueryBuilder/AbstractDMLQueryBuilder.php
index 6a1a290c1..1a20cb8cd 100644
--- a/src/QueryBuilder/AbstractDMLQueryBuilder.php
+++ b/src/QueryBuilder/AbstractDMLQueryBuilder.php
@@ -141,7 +141,7 @@ public function upsert(
      *
      * @psalm-return Iterator|array<iterable<array-key, mixed>>
      */
-    protected function prepareTraversable(Traversable $rows): Iterator|array
+    final protected function prepareTraversable(Traversable $rows): Iterator|array
     {
         while ($rows instanceof IteratorAggregate) {
             $rows = $rows->getIterator();