Using compare rule results in fatal error in getValidationScript function

Easiest way to reproduce this bug is adding this code to any moodle form:

$mform->addElement('text','name1','3',array('size'=>3));
$mform->addElement('hidden', 'name2', '5');
$mform->addRule(array('name1', 'name2'),'You can\'t delete blanks','compare','>=','client',true);//uncommenting this line results in error in getValidationScript

If you uncomment the last line you receive in Moodle 2.4
"Fatal error: Call to a member function getType() on a non-object in Z:\home\moodle\www\lib\formslib.php on line 1818"