Doesn't work with cache enabled

I installed the module and it work all very well but when i enabled caching it sets the language of the first time a page loads and keeps that, even when you select another language.

Something i found out while debugging is that it does set another language in the cookie when you use a drupal_set_message() on that page. This is because that function calls drupal_page_is_cacheable(FALSE);. Implementing this works but then off course you can just disable the caching all together.