diff --git a/lib/Froxlor/Validate/Validate.php b/lib/Froxlor/Validate/Validate.php
index 8332c7eb..a3d83ca5 100644
--- a/lib/Froxlor/Validate/Validate.php
+++ b/lib/Froxlor/Validate/Validate.php
@@ -308,7 +308,7 @@ class Validate
 	 *
 	 * @return bool
 	 */
-	public static function validateSqlInterval(string $interval): bool
+	public static function validateSqlInterval(string $interval = ''): bool
 	{
 		if (!empty($interval) && strstr($interval, ' ') !== false) {
 			/*