[fw-mvc] Zend_Validate error after upgrading to Zend Framework 1.10.1

Zend_Validate::is($value, 'Regex', array('/[^a-v0-9]/'))

It used to work perfectly, now it throws this error:
Warning: include_once() [function.include]: Failed opening 'Regex.php' for inclusion (include_path='/home/user/library:/home/user/application/default/models') in /home/user/library/Zend/Loader.php on line 146

Any idea on what's going on here? Thanks!

Yi