I am trying install a package using cabal-install however the package requies an older version of QuickCheck and one of the required packages requires the latest version: $ cabal fetch Reactive Resolving dependencies... cabal.exe: cannot configure Stream-0.3.1. It requires QuickCheck >=2.0 For the dependency on QuickCheck >=2.0 there are these packages: QuickCheck-2.1 and QuickCheck-2.1.0.1. However none of them are available. QuickCheck-2.1 was excluded because checkers-0.1.3 requires QuickCheck <2.0 QuickCheck-2.1 was excluded because reactive-0.10.5 requires QuickCheck <2.0 QuickCheck-2.1.0.1 was excluded because checkers-0.1.3 requires QuickCheck <2.0 QuickCheck-2.1.0.1 was excluded because reactive-0.10.5 requires QuickCheck <2.0 How can I get around this? I could work around this and install the packages individually. Can I have two versions of a package installed (ie QuickCheck) and will everything get resolved correctly? Mark