Zend XMLRPC Array Depth

Question

Does anyone know if it is possible to change the max depth of an XMLRPC response array for a Zend_XmlRpc_Server? I am returning the following without a problem:

$response = array('level1' => array('level2' => array('level3')));

but as soon as I do this it fails:

$response = array('level1' => array('level2' => array('level3' => array('level4'))));