apt pinning specific dovecot version

[Regan Jelčić]

I currently have the dovecot-core package from wheezy-backports pinned on one of my servers to version '2.2.9', which has been working great. I now want to upgrade that to the newest version under wheezy-backports which is:

dovecot-core (1:2.2.13-11~bpo70+1)
but I can't figure out how to get do it. I've tried a few different formats of the name but apt-get update then apt-get dost-upgrade doesn't pick up the new version - it ignores it when trying to do an update.

This is what I've got in my apt preferences and pin files...

/etc/apt/preferences

Explanation: Stop ALL wheezy-backports updating system.
Package: *
Pin: release a=wheezy-backports,n=wheezy-backports
Pin-Priority: 100 
/etc/apt/preferences.d/dovecot.pref

Explanation: Promote wheezy-backports version of Dovecot only
Package: dovecot-core /2\.2\.9/
Pin: release a=wheezy-backports
Pin-Priority: 500
Can anyone advise how I get it to pull the newer version??

Thanks,