OpenVPN IPv6 RTNETLINK answers: Permission denied

Tue Mar 14 18:45:44 2017 ROUTE_GATEWAY 192.168.100.1/255.255.255.0 IFACE=wlp2s0 HWADDR=h0:43:00:00:0a:8d
Tue Mar 14 18:45:44 2017 ROUTE6: default_gateway=UNDEF
Tue Mar 14 18:45:44 2017 TUN/TAP device tun0 opened
Tue Mar 14 18:45:44 2017 TUN/TAP TX queue length set to 100
Tue Mar 14 18:45:44 2017 do_ifconfig, tt->ipv6=1, tt->did_ifconfig_ipv6_setup=1
Tue Mar 14 18:45:44 2017 /usr/sbin/ip link set dev tun0 up mtu 1500
Tue Mar 14 18:45:44 2017 /usr/sbin/ip addr add dev tun0 10.8.0.3/24 broadcast 10.8.0.255
Tue Mar 14 18:45:44 2017 /usr/sbin/ip -6 addr add 2600:xxx:xx:1f6::1001/64 dev tun0
RTNETLINK answers: Permission denied
Tue Mar 14 18:45:44 2017 Linux ip -6 addr add failed: external program exited with error status: 2
Tue Mar 14 18:45:44 2017 Exiting due to fatal error

net.ipv6.conf.all.disable_ipv6 = 0 
net.ipv6.conf.default.disable_ipv6 = 0 
net.ipv6.conf.lo.disable_ipv6 = 0

sysctl -p