rest - Soundcloud tracks API with license=cc-by-nc returning 400 bad request -

i have php application uses soundcloud api songs specific license: https://developers.soundcloud.com/docs/api/reference#tracks

i make request every license type, 400 bad request error on 1 license=cc-by-nc, example:

http://api.soundcloud.com/tracks/?client_id=apikey&limit=20&license=cc-by-nc&tags=folk 

cc-by-nc in list of available license types on docs, , parameters same licenses. here code of application calling api: https://github.com/antodippo/ccmusicsearch/blob/master/src/ccmusicsearchbundle/service/soundcloudapiservice.php

so think may broken filter , docs may not date. error below:

error_message: "invalid filter.license=cc-by-nc; valid values are: to_share, to_use_commercially, to_modify_commercially, cc-by, cc-by-nc-nd, cc-by-nc-nd-sa, cc-by-nc-sa, cc-by-nd, cc-by-sa"

i tested above , seem work correctly.