Override PHP base dependency in composer

I try to install Laravel 5.1 on a host which only has PHP 5.5.6. While I asked the customer to upgrade, this might be not possible/feasible.

So I am getting:

- This package requires php >=5.5.9 but your PHP version (5.5.6)   does not satisfy that requirement.

on composer.phar install.

Is there a way to do a composer install which ignores this dependency?

I think it should be safe, as there are only bug-fixes from 5.5.6 to 5.5.9.