diff --git a/Civi/DataProcessor/Config/Config.php b/Civi/DataProcessor/Config/Config.php
index cfc3a80e9488df7d801365d43ceb501bb27ed568..3cf9d612cc46b7397e866a4e27af77dc49502729 100644
--- a/Civi/DataProcessor/Config/Config.php
+++ b/Civi/DataProcessor/Config/Config.php
@@ -23,7 +23,7 @@ class Config extends Container {
    */
   public function getCustomFieldsOfCustomGroup($custom_group_id) {
     $customFieldsPerGroup = $this->getParameter('custom_fields_per_group');
-    return $customFieldsPerGroup[$custom_group_id];
+    return $customFieldsPerGroup[$custom_group_id] ?? [];
   }
 
   /**