ifup fails on IPv6 static interface with alias

ifup doesn't trim alias portion of interface from sysctl when configuring IPv6 static addresses:

    # ifup eth0.4000:ucarp
     * Setting up iSCSI targets
       ...done.
    ssh stop/waiting
    ssh start/running, process 23415
    error: "net.ipv6.conf.eth0/4000:ucarp.autoconf" is an unknown key
    Failed to bring up eth0.4000:ucarp.

/etc/network/interfaces:

    iface eth0.4000:ucarp inet6 static
      address 2001:db8::7006
      netmask 64

Note: I'm running uCARP on the IPv4 address family, and expecting it to manage IPv6 address as well via `ifup $IFACE:ucarp` in /usr/share/ucarp/vip-up .

I've tested with /sbin/ifup version 0.7.47.2ubuntu4 copied from a Trusty host and it works fine.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ifupdown 0.7~beta2ubuntu11.1
ProcVersionSignature: Ubuntu 3.5.0-49.74~precise1-generic 3.5.7.32
Uname: Linux 3.5.0-49-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
Date: Tue Jul 22 22:23:10 2014
MarkForUpload: True
ProcEnviron:
 SHELL=/bin/bash
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 LANGUAGE=en_US:
SourcePackage: ifupdown
UpgradeStatus: No upgrade log present (probably fresh install)