Show default lang abbreviation in URL

Does OXID have any built-in function for always showing the lang abbreviation in URLs or does anybody know of a module for this? As an example, my current shop would use the following two links:
http://www.example.com/about-us/
http://www.example.com/fr/a-propos-de-nous/

Are there any settings or modules that would do the following instead:
http://www.example.com/en/about-us/
http://www.example.com/fr/a-propos-de-nous/

If there are no options for this, would anybody else out there find this sort of option useful? Or has anybody else had to deal with this before?

I’ve tried to use the Base URL option in admin under Master Settings>Languages, but didn’t have the desired affect. It changes the URL but also expects a different path to files.

PS. I created a module to force the default abbreviation into the URL, but the way I did it just feels very hack-like.

oxid have iDefSeoLang config option in
Master Settings > Core Settings > SEO > Default language for SEO URLs

That’s the parameter I don’t want (were it possible). The default language selected there is exactly the one with no abbreviation in URLs. For example, if it’s set to English then we have:
http://www.example.com/about-us/
http://www.example.com/fr/a-propos-de-nous/
and if it’s set to French, then we have:
http://www.example.com/en/about-us/
http://www.example.com/a-propos-de-nous/

But I don’t think there’s anyway to override this behaviour and have:
http://www.example.com/en/about-us/
http://www.example.com/fr/a-propos-de-nous/