diff --git a/htdocs/modulebuilder/template/myobject_list.php b/htdocs/modulebuilder/template/myobject_list.php
index 7d09667bd22..a27ddb524a3 100644
--- a/htdocs/modulebuilder/template/myobject_list.php
+++ b/htdocs/modulebuilder/template/myobject_list.php
@@ -106,7 +106,7 @@ $extrafields->fetch_name_optionals_label($object->table_element);
 $search_array_options = $extrafields->getOptionalsFromPost($object->table_element, '', 'search_');
 
 // Default sort order (if not yet defined by previous GETPOST)
-if (!$sortfield) $sortfield = "t.".key($object->fields); // Set here default search field. By default 1st field in definition.
+if (!$sortfield) { reset($object->fields); $sortfield="t.".key($object->fields); }   // Set here default search field. By default 1st field in definition. Reset is required to avoid key() to return null.
 if (!$sortorder) $sortorder = "ASC";
 
 // Initialize array of search criterias