Problem loading js from facebook with wrong culture code

After network activating Ultimate Facebook I received the following JS error on all my pages
"FB is not defined"

After some quick research with Fiddler I found that the plugin loads the following .js file:

This request gives the following response
/* "nl" is not a valid locale. */

Based on this information I tried loading the url in a browser, which returned a error. After changing the url to a different locale (nl-NL) the .js file is returned from facebook.

I tried changing the locale from Automatic to Dutch and English (UK), but that didn't change the request.

Any idea what to do next?