Symfony fails on sfValidatorRegex

Question

I'm using the following line:

$this->validatorSchema['name'] = new sfValidatorRegex(
array('pattern' => '<my_regex>', 'must_match' => false), 
array('invalid' => 'Invalid name'));

But "must_match" option is not working and I don't know why. Whatever I use true or false, it works like always: detect the expression and if it's on the text, it will approve the name.

Thanks.