On a debian squeeze host I had to upgrade a package that pulls more than 40 dependencies. The target version was provided by squeeze-backports. I got sure that squeeze-backports was somewhere in /etc/apt/sources.list.d/, and so available. Then I specified the backports candidate version: sudo apt-get install package=bpo_version No cigar. Two of the pulled packages didn't exist in squeeze. But why was apt trying to get them from squeeze, and not from squeeze-backports, to which package=bpo_version belongs? The thing is that apt has been designed to do that. The solution is to indicate explicitely the target release with the -t option: sudo apt-get -t squeeze-backports install package=bpo_version and that works smoothly. Problem solved then? Yes, unless you're using Puppet, which doesn't allow you to specify the target release. After spending some time with apt pinning , I've decided to script the update as an Exec in a manifest: exec {'install...