diff --git a/src/Model/Quote/Item/Processor.php b/src/Model/Quote/Item/Processor.php
index 162f175..35890a6 100644
--- a/src/Model/Quote/Item/Processor.php
+++ b/src/Model/Quote/Item/Processor.php
@@ -37,7 +37,7 @@ public function prepare(Item $item, DataObject $request, Product $candidate): vo
         if ($request->getResetCount() && !$candidate->getStickWithinParent() && $item->getId() == $request->getId()) {
             $item->setData(CartItemInterface::KEY_QTY, 0);
         }
-        $item->setQty($candidate->getCartQty());
+        $item->addQty($candidate->getCartQty());
 
         if (!$item->getParentItem() || $item->getParentItem()->isChildrenCalculated()) {
             $item->setPrice($candidate->getFinalPrice());