Can't create site with language other than english

I'm trying to create a site on a platform using a custom installation profile for which I have added drupal-7.41.fr.po in the translations directory. I can select "French (Français)" in the language options , but upon saving the site I get the error "Please fill in a valid language".

I also tried copying drupal-7.41.fr.po in profiles/minimal/translations and installing using that profile, to no avail.

It seems the hosting_get_profile_languages function returns both 'en' and 'fr' when it is called with $platform = NULL (when building the form in hosting_site_form), but only returns 'en' when $platform != NULL (when called from hosting_site_validate).

I also tried creating a new platform that would have the translation file upon its creation, but it didn't help at all.

Am I missing something?!