WeeChat does not use IPv6

I have a WeeChat version 1.5 installed on Debian 8.5 with irc.server.freenode.ipv6 option set to on: 10:57:15 weechat | [server] (irc.conf) 10:57:15 weechat | irc.server.freenode.ipv6 = on (default: (undefined)) 10:57:15 weechat | 10:57:15 weechat | 1 option (matching with "irc.server.freenode.ipv6") This should force WeeChat to prefer IPv6 over IPv4. irc.freenode.net has IPv6 AAAA records present: $ dig @8.8.8.8 -t AAAA irc.freenode.net +noall +short chat.freenode.net. 2a00:1a28:1100:11::42 2a01:270:0:666f::1 2a01:7e00::f03c:91ff:fee2:413b 2001:6b0:e:2a18::118 $ ..and for example I'm able to ping irc.freenode.net over IPv6: $ ping6 -nc 4 irc.freenode.net PING irc.freenode.net(2001:5a0:3604:1:64:86:243:181) 56 data bytes 64 bytes from 2001:5a0:3604:1:64:86:243:181: icmp_seq=1 ttl=51 time=141 ms 64 bytes from 2001:5a0:3604:1:64:86:243:181: icmp_seq=2 ttl=51 time=141 ms 64 bytes from 2001:5a0:3604:1:64:86:243:181: icmp_seq=3 ttl=51 time=142 ms 64 bytes from 2001:5a0:3604:1:64:86:243:181: icmp_seq=4 ttl=51 time=142 ms --- irc.freenode.net ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3004ms rtt min/avg/max/mdev = 141.567/141.903/142.081/0.431 ms $ However, when I try to connect to irc.freenode.net in WeeChat, then IPv6 is not even tried (checked with tcpdump). Even if I reject connections on IPv4 to TCP port 6667, then IPv6 is not tried. I assume that the problem is not with the WeeChat (I even tried with different versions). Any ideas, what might cause such behavior?