locale_language_from_url() doesn't work because $_GET['q'] was modified

I found locale_language_from_url() needs a work-around. This was with Drupal 7.8, but presumably true of other D7 versions. The following code works for me:

    // Due to an apparent bug somewhere in Drupal language processing,
    // locale_language_from_url() doesn't work because it expects $_GET['q'] to
    // include the language prefix, but the prefix has already been removed.
    // As a work-around, temporarily set $_GET['q'] to request_path().
    // This works because request_path() statically caches the original value.
    $languages = language_list();
    $saveq = $_GET['q'];
    $_GET['q'] = request_path();
    $url_language_id  = locale_language_from_url($languages);
    $_GET['q'] = $saveq;

I know that the same language value can normally be accessed via the global $language object, but in my case I needed to detect language from url during bootstrap, when $language is not initialised.

It also seems that this is probably only an issue when serving cached pages:

bootstrap.inc #2218:

      // Restore the metadata cached with the page.
      $_GET['q'] = $cache->data['path'];

So, this seems like a bug. Should I make a patch for locale.inc so that locale_language_from_url() uses request_path() ? Or is the underlying issue that the page $cache->data['path'] should really hold the original path with prefix?