Altiris 7.5 MSD Supersedence - does it work?

Hi all,

I've built an MSD policy to deliver an MSI. Many machines have an earlier version (different GUID) installed and installing the later version does nothing to the earlier one. Hah I thought - supersedence! Added a package with a default uninstall command to the earlier version and set it as superseded by the later one. In the policy for the new version I ticked "Automatically upgrade..." The policy gets delivered to the client, it shows the old version as "Detected" but apparently does nothing about it. It then goes on to install the new. Have I missed something?

Thanks

Martin