Auth url webhooks not working

Hi guys,

Sorry if I'm missing something obvious, but I really can't make authentication url working. I have Icecast configs:

    <mount>
        <mount-name>/aac_high</mount-name>
        <authentication type="url">
        <option name="listener_add" value="http://localhost:3000/api/v1/listeners/add"/>
        <option name="listener_remove" value="http://localhost:3000/api/v1/listeners/remove"/>
        <option name="auth_header" value="icecast-auth-user: 1"/>
        </authentication>
    </mount>

By calling /aac_hight I got 401 despite server is configured to return correct header:

$ curl http://localhost:8000/aac_high
<?xml version="1.0"?>
<report xmlns="http://icecast.org/specs/reportxml-0.0.1" version="0.0.1"><incident><state definition="25387198-0643-4577-9139-7c4f24f59d4a"><text>You need to authenticate</text></state></incident><extension application="http://icecast.org/specs/legacy-icestats"><icestats xmlns="http://icecast.org/specs/legacystats-0.0.1"><modules/></icestats></extension></report>

In Icecast's error.log I'm getting:

[2020-11-05  11:44:02] INFO auth/queue_auth_client auth on /aac_high has 1 pending
[2020-11-05  11:44:02] INFO auth_url/url_add_client client auth (http://localhost:3000/api/v1/listeners/add) failed with ""
[2020-11-05  11:44:02] WARN reportxml/reportxml_database_build_report No matching definition for "25387198-0643-4577-9139-7c4f24f59d4a"

So, looks like it is trying to reach http://localhost:3000/api/v1/listeners/add but in server logs I don't see any incoming request at all. Callback on localhost:3000 working fine:

$ curl -v -X POST  http://localhost:3000/api/v1/listeners/add
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 3000 (#0)
> POST /api/v1/listeners/add HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< icecast-auth-user: 1
< Server: Dominion
< Date: Thu, 05 Nov 2020 12:19:24 GMT
< Connection: keep-alive
< Content-Length: 0
<
* Connection #0 to host localhost left intact

Icecast is built from master branch, additional info:

$ ./icecast -v
Icecast 2.4.99.2

$ cat /etc/os-release
NAME="Ubuntu"
VERSION="18.04.3 LTS (Bionic Beaver)"

Will appreciate any hint what is going wrong. Thanks!