How to activate French default page for French domain

Hi, I built a multilanguage (Dutch - French) website with Middleman:

www.armoede-in-belgie.be

repository

All is working well, but this website has two domains:

armoede-in-belgie.be (Dutch)
pauvrete-en-belgique.be (French)

The problem I have is that when going to the French domain, the Dutch template (index.nl.html.erb) is loaded by default:

www.pauvrete-en-belgique.be

The visitor can change the template to French changing the language via a multilanguage selector, but it would be more convenient if the French template is shown right away when surfing to the French domain (pauvrete-en-belgique.be).

Is there a way to enable this in Middleman?

Thanks for your help,

Anthony