ddns with dhcp6 not working

Kea 2.0.0 DDNS updates are not working with DHCP6. IPv6 address is assigned but nothing happens with D2. I've tried a tcpdump on lo0, but no traffic to 53001. If I try the same with DHCP4 everything is fine and DDNS is updated.

config snippets:

{
"DhcpDdns":
{
  "ip-address": "127.0.0.1",
  "port": 53001,
  "control-socket": {
      "socket-type": "unix",
      "socket-name": "/tmp/kea-ddns-ctrl-socket"
  },
  "tsig-keys": [
    {
      "name": "dhcp-update.",
      "algorithm": "hmac-md5",
      "secret": "replaced"
    }
  ],
  "forward-ddns" : {
      "ddns-domains": [
          {
              "dns-servers": [
                  {
                      "ip-address": "2002:629:2131:2300::53:1",
                      "port": 53
                  }
              ],
              "key-name": "dhcp-update.",
              "name": "lan6.abc.net."
          },
....

{
"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ "vmx0/2002:629:2131:2300::547:11" ]
    },
    "control-socket": {
        "socket-type": "unix",
        "socket-name": "/tmp/kea6-ctrl-socket"
    },
    "dhcp-ddns" : {
        "enable-updates" : true,
        "server-ip": "127.0.0.1",
        "server-port":53001
    },
...
    "subnet6": [
        {
            "subnet": "2002:629:2131:445C::/64",
            "id": 2016,
            "rapid-commit": true,
            "pools": [ { "pool": "2002:629:2131:445C::4-2002:629:2131:445C::80", "client-class": "registered-server1" },
                       { "pool": "2002:629:2131:445C::81-2002:629:2131:445C::FF", "client-class": "registered-server2" } ],
            "reservations-global": true,
            "reservations-in-subnet": false,
            "ddns-override-client-update": true,
            "ddns-override-no-update": true,
            "ddns-send-updates": true,
            "ddns-qualifying-suffix": "lan6.abc.net.",
            "hostname-char-set": "[^A-Za-z0-9.-]",
            "hostname-char-replacement": "x"
        }
    ],
...