diff --git a/resources/functions.php b/resources/functions.php
index 25ea6ceb75..322c5e6793 100644
--- a/resources/functions.php
+++ b/resources/functions.php
@@ -638,7 +638,7 @@ if (!function_exists('th_order_by')) {
 	 *
 	 * @return string The generated HTML for the table header cell with ordering functionality.
 	 */
-	function th_order_by(string $field_name, string $column_title, string $order_by, string $order, string $app_uuid = '', string $css = '', string $http_get_params = '', string $description = ''): string {
+	function th_order_by(string $field_name, string $column_title, string $order_by, string $order, ?string $app_uuid = '', ?string $css = '', ?string $http_get_params = '', ?string $description = ''): string {
 		global $text;
 		if (is_uuid($app_uuid) > 0) {
 			$app_uuid = "&app_uuid=" . urlencode($app_uuid);