IPv6 client shows as docker host IPv4 in logs

I have a Caddy docker listening on 80 and 443, both port published on the host (with -p).

When an IPv6 client connects to caddy, in the logs I see the docker host IPv4 address (in my case 172.26.0.1) instead of the real client's IPv6.

I have a custom network bridge to connect caddy to an application container via the proxy directive.

This is my Caddyfile:

```
http://site1 {
tls off
redir https://{host}{uri}
}
https://site1 {
proxy / app-container:8080
tls email@address.com
root /srv
log / stderr {combined}
}
```

What am I missing?