Administration - Installation - Core: ILIAS 5.4.8 Cronjob issue (PHP)

Hello,

since we upgrade ILIAS to Version 5.4.8 our Cronjob in ILIAS isn´t working anymore.
Env:
Ilias: 5.4.8
PHP: 7.3.11
Crontab:  /bin/php /volume1/web/ilias/cron/cron.php [user] [password] [clientid]

Starting the cronjob is successfully. User, Password and clientid get forwarded to the cron.php and the cron.php start running. 

After a short time i get the following error:

PHP Parse error: syntax error, unexpected ':', expecting ';' or '{' in /volume1/web/ilias/Services/Utilities/classes/class.ilUtil.php on line 2576

Parse error: syntax error, unexpected ':', expecting ';' or '{' in /volume1/web/ilias/Services/Utilities/classes/class.ilUtil.php on line 2576

In the php File ilUtil.php on the line 2576 i have the following code

public static function getClientIdByString(string $clientId) : \ILIAS\Data\ClientId
{
$df = new \ILIAS\Data\Factory;

return $df->clientId($clientId);
}

Can anyone help me with fixing the error, please?

Thanks and best regards,
Stefan