Save as Docbook XML

I am trying to save a structured FM file as DocBook xml, But it is not giving me DocBook output, just regular XML.

Here is my code, my best guess is line 13 is the issue.

function saveAsDBXML (doc, saveFolderName){    $.writeln("SAVE_XML: " + doc.Name);    var params = GetSaveDefaultParams();    var returnParamsp = new PropVals();       var fileName = String(doc.Name.match(/[\w\.]+$/))    var saveName = saveFolderName + fileName.replace(/\.[^\.\\]+$/,".xml");       var i = GetPropIndex(params, Constants.FS_FileType);    params[i].propVal.ival = Constants.FV_SaveFmtXml;    var i = GetPropIndex(saveParams, Constants.FS_StructuredSaveApplication);    saveParams.val[i].propVal.sval = "DocBook";    doc.Save (saveName, params, returnParamsp);    return saveName
}

Also tried:

saveParams.val[i].propVal.sval = "DocBook 2.1";

and

saveParams.val[i].propVal.sval = "XDocBook";

Thanks

Ethan