socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument on OpenBSD

Running the geoip2 v9_16 system test on OpenBSD produces the following warning:

I:geoip2:checking Country database by code using IPv6 (8)
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument
socket.c:5111: setsockopt(20, IPV6_V6ONLY) failed: Invalid argument

Its invoked by running dig seven times: dig +tcp +short -p ${PORT} @fd92:7065:b8e:ffff::2 -6 txt example -b fd92:7065:b8e:ffff::$i.

The test otherwise passed.

It's with us for a long time as it's present in 9.11.37.