Watson-js spanish SpeechToText not working

Question

I haven't been able to set the language to spanish in the watson-js speech to text api. I think I've tried every variation of the following line:

, xarg: "Content-Language=es-us"

Has anybody achieved this? How?

    exports.ATT_CREDS = {
    client_id:"client_id"
    , client_secret:"client_secret"
    , access_token:"access_token"
    , scope: "SPEECH"
    , context: "Generic"
    , access_token_url: "https://api.att.com/oauth/token"
    , api_domain: "api.att.com"
    , content_type: "audio/wav"
    , xarg: "Content-Language=es-us"
};

Answer 1

Problem solved: documentation on watson's API was wrong. After a couple of emails it got corrected. It was something with the xarg variable. It's updated now.

AT&T Speech API