How can I tell the Haskell compiler where to find module Control.Monad.Error? After building GHC 7.6.3 and Haskell Platform 2013.2 on Red Hat Linux 6, I found that 'cabal install cabal-install' fails when it attempts to build library HTTP-4000.2.11 because the Haskell compiler cannot find module Control.Monad.Error. ******************************************************* * Installation completed successfully. * * Programs installed into: * /usr/local/bin * * Now do "cabal update" to initialize the package list * * Additional packages may be found at http://hackage.haskell.org * or via "cabal list <pattern>" * * Use "cabal install <foo>" to install additional packages * ******************************************************* [dmahar@dmahar haskell-platform-2013.2.0.0]$ cabal update Downloading the latest package list from hackage.haskell.org Note: there is a new version of cabal-install available. To upgrade, run: cabal install cabal-install [dmahar@dmahar haskell-platform-2013.2.0.0]$ cabal install cabal-install Resolving dependencies... Configuring HTTP-4000.2.11... Building HTTP-4000.2.11... Preprocessing library HTTP-4000.2.11... Network/Stream.hs:35:8: Could not find module `Control.Monad.Error' There are files missing in the `mtl-2.1.2' package, try running 'ghc-pkg check'. Use -v to see a list of the files searched for. Failed to install HTTP-4000.2.11 cabal: Error: some packages failed to install: HTTP-4000.2.11 failed during the building phase. The exception was: ExitFailure 1 cabal-install-1.18.0.2 depends on HTTP-4000.2.11 which failed to install. Thank you, Derek