diff --git a/lib/internal/Magento/Framework/Webapi/ServiceInputProcessor.php b/lib/internal/Magento/Framework/Webapi/ServiceInputProcessor.php
index d0ed69bfdadd6..76726cde0c7fb 100644
--- a/lib/internal/Magento/Framework/Webapi/ServiceInputProcessor.php
+++ b/lib/internal/Magento/Framework/Webapi/ServiceInputProcessor.php
@@ -260,7 +260,7 @@ private function processCustomAttribute($customAttribute)
             throw new SerializationException(new Phrase('There is an empty custom attribute specified.'));
         } elseif (!$customAttributeCode) {
             throw new SerializationException(new Phrase('A custom attribute is specified without an attribute code.'));
-        } elseif (!isset($customAttribute[AttributeValue::VALUE])) {
+        } elseif (!array_key_exists(AttributeValue::VALUE, $customAttribute)) {
             throw new SerializationException(
                 new Phrase('Value is not set for attribute code "' . $customAttributeCode . '"')
             );