defining static IPv6 addresses in /etc/network/interfaces

[Jason White <jason@jasonjgw.net>]

Hello,

I have a static IPv4 address defined in /etc/network/interfaces, as in
iface eth1 inet static
address 192.168.0.2
netmask 255.255.255.0
gateway 192.168.0.1

If I now try to add a static IPv6 interface:

interface eth1 inet6 static
address 2001:470:801f::1
netmask 64
gateway 2001:470:1f05:15a::1

I get a "duplicate option" error whenever I try to bring the interface up or
down with ifup/ifdown.

This is a reasonably up to date Debian Sid system.

Am I configuring this incorrectly, or is there a bug?

Suggestions welcome.