inet6 loopback interfaces and /etc/network/interfaces

Hi,

I am trying to bring up an IPv6 address on a loopback interface:
2001:XXX:0:FFFA::8/128 using ifup(8) and /etc/network/interfaces.

root@mana:~# ifup lo:10
SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
Failed to bring up lo:10.

/etc/network/interfaces:

--
# The loopback network interface

auto lo
iface lo inet loopback
iface lo inet6 loopback

# IPv6 LAN address

iface eth0 inet6 static
address 2001:XXX:0:FFFD::66
netmask 64
gateway 2001:XXX:0:FFFD::1

# IPv6 loopback 10

iface lo:10 inet6 static
address 2001:XXX:0:FFFA::8
netmask 128
--

I have tried various combinations of static, loopback, manual as the
inet6 interface method, read, and reread the ifup(8), interfaces(5)
man pages, but no luck.

Adding it manually works, no problem:

root@mana:~# ifconfig lo:10 inet6 add 2001:XXX:0:FFFA::8/128
root@mana:~# ip addr show | grep -i FFFA
inet6 2001:XXX:0:fffa::8/128 scope global

Anyone care to try see if they can get this to work?

OS:

root@mana:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 7.04
Release: 7.04
Codename: feisty

Cheers,
Jaco