create-data-change-event-subscription response is not in XML format despite request was "application/xml"

following "Change event notification subscription" procedure on odl wiki https://wiki.opendaylight.org/view/OpenDaylight_Controller:MD-SAL:Restconf:Change_event_notification_subscription

setup environment:
------------------
1. start odl distribution-karaf-0.5.0-Boron
2. install features:
feature:install odl-restconf
feature:install odl-dlux-all
feature:install odl-ovsdb-southbound-impl
log:set DEBUG org.opendaylight.netconf.sal

when I send create-data-change-event-subscription request (see postman collection) with Content-Type "application/xml" response is in JSON format

request:
<input xmlns="urn:opendaylight:params:xml:ns:yang:controller:md:sal:remote">
<path xmlns:a="urn:TBD:params:xml:ns:yang:network-topology">/a:network-topology</path>
<datastore xmlns="urn:sal:restconf:event:subscription">CONFIGURATION</datastore>
<scope xmlns="urn:sal:restconf:event:subscription">BASE</scope>
</input>

response:
{
"output":

{ "stream-name": "data-change-event-subscription/network-topology:network-topology/datastore=CONFIGURATION/scope=BASE" }

}