diff --git a/app/code/Magento/ConfigurableProduct/Model/Quote/Item/CartItemProcessor.php b/app/code/Magento/ConfigurableProduct/Model/Quote/Item/CartItemProcessor.php
index 798348087dffc..785b2062eef5c 100644
--- a/app/code/Magento/ConfigurableProduct/Model/Quote/Item/CartItemProcessor.php
+++ b/app/code/Magento/ConfigurableProduct/Model/Quote/Item/CartItemProcessor.php
@@ -59,7 +59,7 @@ public function convertToBuyRequest(CartItemInterface $cartItem)
             if (is_array($options)) {
                 $requestData = [];
                 foreach ($options as $option) {
-                    $requestData['super_attribute'][$option->getOptionId()] = $option->getOptionValue();
+                    $requestData['super_attribute'][$option->getOptionId()] = (string) $option->getOptionValue();
                 }
                 return $this->objectFactory->create($requestData);
             }