specify title tag from another module?

Hi,

I am developing a custom module that uses HTML title tag differently from page title. In doing that, I've implemented foo_preprocess_page() to override $vars['head_title']. However, $vars['head_title'] seems to get overridden again by page_title module. So, is there a way to specify the HTML title tag from another module? Thanks for page_title and for any hints. :)