Hello, I "unregistered" unix-2.3.0.0. Now I cannot rebuild the Unix package. Please see the below log: vigalchin@ubuntu:~$ ghc-pkg latest unix unix-2.2.0.0 vigalchin@ubuntu:~$ ghc-pkg describe unix name: unix version: 2.2.0.0 license: BSD3 copyright: maintainer: libraries@haskell.org stability: homepage: package-url: description: This package gives you access to the set of operating system services standardised by POSIX 1003.1b (or the IEEE Portable Operating System Interface for Computing Environments - IEEE Std. 1003.1). . The package is not supported under Windows (except under Cygwin). category: author: exposed: True exposed-modules: System.Posix System.Posix.DynamicLinker.Module System.Posix.DynamicLinker.Prim System.Posix.Directory System.Posix.DynamicLinker System.Posix.Env System.Posix.Error System.Posix.Files System.Posix.IO System.Posix.Process System.Posix.Process.Internals System.Posix.Resource System.Posix.Temp System.Posix.Terminal System.Posix.Time System.Posix.Unistd System.Posix.User System.Posix.Signals System.Posix.Signals.Exts System.Posix.Semaphore System.Posix.SharedMem System.Posix.MQueue hidden-modules: import-dirs: /usr/local/lib/unix-2.2.0.0/ghc-6.8.2 library-dirs: /usr/local/lib/unix-2.2.0.0/ghc-6.8.2 hs-libraries: HSunix-2.2.0.0 extra-libraries: util dl extra-ghci-libraries: include-dirs: /usr/local/lib/unix-2.2.0.0/ghc-6.8.2/include includes: HsUnix.h execvpe.h depends: base-3.0.1.0 directory-1.0.0.0 hugs-options: cc-options: ld-options: framework-dirs: frameworks: haddock-interfaces: /usr/local/share/doc/unix-2.2.0.0/html/unix.haddock haddock-html: /usr/local/share/doc/unix-2.2.0.0/html vigalchin@ubuntu:~$ vigalchin@ubuntu:~/FTP/Haskell/unix-2.2.0.0$ runhaskell Setup.hs configure unknown package: unix-2.3.0.0 In my .cabal file, I have specified the version as 2.2.0.0, 2.3.0.0 and 2.4.0.0 all with the same results: "unknown package: unix-2.3.0.0" Vasili