diff --git a/Block/Adminhtml/Form/Field/VendorMapping.php b/Block/Adminhtml/Form/Field/VendorMapping.php
index 32abffb..2bafe9f 100644
--- a/Block/Adminhtml/Form/Field/VendorMapping.php
+++ b/Block/Adminhtml/Form/Field/VendorMapping.php
@@ -50,10 +50,13 @@ class VendorMapping extends AbstractFieldArray
         $result = [];
         /** @var DataObject $row */
         foreach (parent::getArrayRows() as $key => $row) {
-            // Ensure row IDs are prefixed with a non-numeric character
+            // Ensure row IDs are prefixed with underscore to make valid CSS selectors
+            // CSS IDs cannot start with a number
             if (is_numeric($key)) {
-                $key = 'row_' . $key;
+                $key = '_' . $key;
             }
+            // Also set the _id property in the row data for proper rendering
+            $row->setData('_id', $key);
             $result[$key] = $row;
         }
         return $result;