Hi Does pjsip have support for RFC5031?, For emergency call I have to send INVITE with header: "TO URN" with "urn:sercice:sos". Do you know how to do this via pjsua2 api? I try something like this: final SipHeaderVector headerVector prm.getTxOption().getHeaders(); SipHeader sosheader = new SipHeader(); sosheader.setHName("To URN"); sosheader.setHValue("URN:service:sos"); headerVector.add(sosheader); prm.getTxOption().setHeaders(headerVector); super.makeCall(dst_uri, prm); it's add, but also add with normal "To" header with 112@domain etc. and this is wrong. It is possible to send INVITE without "To" header? Regards Andrzej [https://tools.ietf.org/html/rfc5031]