no dnstap messages with unix socket

Summary

Hello, I try to use the dnstap feature but no dnstap messages are generated with a unix socket. if a use the dnstap-output file then dnstap messages are generated.

BIND version used

Bind 9.16 on CentOS8 - https://copr.fedorainfracloud.org/coprs/isc/bind/

/opt/isc/isc-bind/root/usr/sbin/named -v BIND 9.16.10 (Stable Release) id:fac8def

I have also tested with bind 9.11 and it's work fine so I don't know what i'm doing wrong.

Steps to reproduce

install the dnstap receiver and start-it in unix mode

python3 -m pip install dnstap_receiver
su - named -s /bin/bash -c "dnstap_receiver -u /var/opt/isc/scls/isc-bind/named/data/dnstap.out -v"

Configure named with dnstap and restart-it

options {
        directory "/var/opt/isc/scls/isc-bind/named/data";
        listen-on { 127.0.0.1; };
        listen-on-v6 { ::1; };
        dnssec-validation auto;

        dnstap-identity "bind";
        dnstap-version "xxx";
        dnstap-output unix "dnstap.out";
        dnstap { all; };
}

When I make a "dig", no dnstap messages are received, nothing happened. I have also tested with the dnstap in go and it's the same thing.