New IPv6 settings in rc.conf

I updated my router to the latest -CURRENT yesterday and now I'm getting an 
error on startup from ifconfig saying the the IPv6 addresses I've configured 
are wrong ("bad value"). The settings I've got in rc.conf are:

# IPv4 setup
defaultrouter="a.b.c.d"
gateway_enable="YES"
ifconfig_vr0="a.b.c.d netmask 255.255.248.0 up"
cloned_interfaces="bridge0"
ifconfig_bridge0="addm dc0 addm dc1 addm dc2 addm dc3 192.168.1.1 netmask 
255.255.255.0 up"
ifconfig_dc0="up"
ifconfig_dc1="up"
ifconfig_dc2="up"
ifconfig_dc3="up"

# IPv6 setup
ipv6_prefer="YES"
ipv6_gateway_enable="YES"
ipv6_defaultrouter="2001:abcd:abcd:abc::x"

gif_interfaces="gif0 gif1"
gifconfig_gif0="a.b.c.d e.f.g.h"
gifconfig_gif1="a.b.c.d i.j.k.l"
ifconfig_gif0_ipv6="2001:abcd:abcd:abc::x abcd:abc:abcd:abc::x prefixlen 128"
ifconfig_gif1_ipv6="2a01:abcd:a:bc::x abcd:abc:x:ab::x prefixlen 128"

# if_bridge doesn't have a link-local address by default, so add one
ifconfig_bridge0_ipv6="fe80::2%bridge0 prefixlen 64"
ifconfig_bridge0_ipv6_alias0="2001:abcd:abcd:abcd::x"

# DHCP, DHCPv6 and rtadvd settings follow


I can manually run ifconfig once the systems running so I guess I've missed 
out a required setting somewhere?

-- 
Bruce Cran