Making a lookup for an artist in JSON (fmt=json) consistently results in the data without the gender.

E.g.,

Bob Dylan (gender missing)

http://musicbrainz.org/ws/2/artist/72c536dc-7137-4477-a521-567eeb840fa8?fmt=json

Britney Spears (gender missing)

http://musicbrainz.org/ws/2/artist/45a663b5-b1cb-4a91-bff6-2bef7bbfdd76?fmt=json

Bob Marley (gender missing)

http://musicbrainz.org/ws/2/artist/ed2ac1e9-d51d-4eff-a2c2-85e81abd6360?fmt=json

I have not yet found a 'person' artist (not group) that contains the gender when using fmt=json.