Sipml5 Transfer with configuration params

Question

In my SIPML5 code, I use the transfer method which works fine:

oConfigCall = {
  sip_headers: [{
      name: 'X-SicaId',
      value: "1",
      session: true
    },
    {
      name: 'X-RecordingFile',
      value: "123.wav",
      session: true
    }
  ]
};

//22 is the prefix in my dial plan 
oSipSessionCall.transfer("22" + s_destination, oConfigCall)

But asterisk doesn't receive the headers, they're empty. In the original INVITE, it does receive the headers, but not in the transfer.

How can I send custom headers with my transfer request?