diff --git a/includes/admin/core/class-admin-forms.php b/includes/admin/core/class-admin-forms.php
index 6f4cb86d..92355732 100644
--- a/includes/admin/core/class-admin-forms.php
+++ b/includes/admin/core/class-admin-forms.php
@@ -125,6 +125,9 @@ if ( ! class_exists( 'um\admin\core\Admin_Forms' ) ) {
 							'target' => array(),
 							'class' => array(),
 						),
+						'button' => array(
+							'class' => array(),
+						),
 						'i' => array(
 							'class' => array(),
 						),