How to disable ip6 lookups in unbound?

I attempted to disable IPv6 lookups in unbound through these options: do-ip6: no prefer-ip6: no Really prefer-ip6 should only take effect when do-ip6 is yes. In any case, I use tcpdump to dump the traffic and I still see IPv6 queries being issued to my forwarding server. If I have disabled it, why is unbound still attempting to do IPv6? Is there another hidden option that is silently enabling it?