incorrect language tag error for "sgs"

Hello all,

When validating http://www.wikipedia.org/ (
http://validator.w3.org/check?uri=http%3A%2F%2Fwww.wikipedia.org%2F ) I
get an error saying

"Bad value sgs for attribute lang on element a: Bad ISO language part in
language tag."

However, according to
http://www.iana.org/assignments/language-subtag-registry "sgs" was added
in july.

Could you please update the corresponding code or list?

-- 
Regards,
Jeroen
( not affiliated with WP, just working on http://vldtr.com/top10/ )