Resolver-conf doesn't check if there is disabled IPv6 for WAN

In Foris's WAN tab, I have disabled IPv6 and when I want to use forwarding to one of suggested DNS forwarder, it tries to reach those DNS servers via IPv6 and it floods syslog with messages like:

2019-08-18 18:50:21 err unbound[]: [17527:0] error: outgoing tcp: connect: Permission denied for 2606:4700:4700::1111 port 853
2019-08-18 18:50:21 err unbound[]: [17527:0] error: outgoing tcp: connect: Permission denied for 2606:4700:4700::1001 port 853
2019-08-18 18:50:21 err unbound[20689]: Last message '[17527:0] error: out' repeated 1 times, suppressed by syslog-ng on turris