diff --git a/app/code/Magento/Bundle/Model/Product/Type.php b/app/code/Magento/Bundle/Model/Product/Type.php
index afcb09f2f43fe..b81f9f5d31bd6 100644
--- a/app/code/Magento/Bundle/Model/Product/Type.php
+++ b/app/code/Magento/Bundle/Model/Product/Type.php
@@ -822,7 +822,7 @@ private function multiToFlatArray(array $array)
             if (is_array($value)) {
                 $flatArray = array_merge($flatArray, $this->multiToFlatArray($value));
             } else {
-                $flatArray[$key] = $value;
+                $flatArray[] = $value;
             }
         }