canvas url wrong (missing slash) when i18n module used

Whenever I do a change in drupal the Facebook app settings are updated with a URL that lacks a slash ("/")

This is what it should be: http://domain.tld/sv/fb_cb/appid/
This is what is set currently: http://domain.tld/svfb_cb/appid/

Note the missing slash before "fb_cb/"

"sv" is the lang identifier for sweden.

i18n and site in general is working for everything else.

This looks like a great module - Thank you!