Setting SQUISH_IPV6=0 still results in AF_INET6 created

Squish version: 9.0.0.

I'm running my application on yocto linux through "startaut" to listen to squish connections.

During the startup I can see error like:

Could not listen on port <myport> for incoming connections, attaching to this process will not work.

If I run strace, I can further see that the error is:

socket(AF_INET6, SOCK_STREAM, IPPROTO_IP) = -1 EAFNOSUPPORT (Address family not supported by protocol)

As documented in https://doc.qt.io/squish/environment-variables.html, I've tried to set environment variable SQUISH_IPV6=0 to prevent using IPv6. However, it does not have an effect, and I can see that the process environment (/proc/`pidof myapp`/environ) does not list the SQUISH_IPV6 variable at all - as if it was unset.

The function unsetenvIfSquishEnv() in startaut main.cpp looks interesting. Is it possibly missing whitelisting of the new environment variable?