diff --git a/app/code/core/Mage/Adminhtml/Model/Config/Data.php b/app/code/core/Mage/Adminhtml/Model/Config/Data.php
index 90fdb895c6d..d6d881fe18a 100644
--- a/app/code/core/Mage/Adminhtml/Model/Config/Data.php
+++ b/app/code/core/Mage/Adminhtml/Model/Config/Data.php
@@ -138,7 +138,7 @@ public function save()
                     }
                 }
 
-                $backendClass = $helper->getBackendModelByFieldConfig($fieldConfig);
+                $backendClass = $fieldConfig ? $helper->getBackendModelByFieldConfig($fieldConfig) : false;
                 if (!$backendClass) {
                     $backendClass = 'core/config_data';
                 }