Hi Maciej, that's why I started hack-nix. You can patch dependencies easily. However you have to install the Nix package manager. It also works with lates versions only because the dependency solves is written in Nix itself. Which package is causing trouble to you? We can't expect package maintainers to test everything. So it must be people like you and me who fixes those changes. The way to go is make hackage allow changing constraints on the fly notifying the author that he can update his repository. This will work in most cases. Bumping versions because a dependency has changed is bad as well. This will cause to much overhead (and it dosen't solve the problem because the old package is still wrong). Specifying dependencies must be decoupled from bumping versions. It's because dep specs do depend on the "world" which can change.. At least that's what I think. If you're interested in Nix and hack-nix I can show you how everything works using an SSH session. Marc Weber