Default language not set when not using path prefix

I have a site in English and French with English as the default language.

There is no path prefix for English. The path prefix for French is 'fr'.

The detection methods enabled are URL, Cookie and Default.

If the language cookie is set to 'fr' and English is chosen using the language switcher, the cookie is not overwritten.

In the function _language_cookie_get_language() in language_cookie.module I modified

    if ($provider_id == LANGUAGE_COOKIE_NEGOTIATION) {
      return FALSE;
    }

to

    if ($provider_id == LANGUAGE_COOKIE_NEGOTIATION) {
      break;
    }

to ensure the cookie is overwritten with the default language.