cabal-install calls setup with unrecognised distpref flag

Hello all, Recently, while developing a package here in the group, we changed the build-type from "Simple" to "Custom" to allow for "cabal test". The Setup.hs simply calls defaultMainWithHooks with simpleUserHooks where runTests has been redefined. The problem is that this change gives me the following error when invoking "cabal build" (after invoking "cabal configure"): setup.exe: Unrecognised flags: --distpref=dist runhaskell Setup.hs build works fine, though. This happens on a win64 machine, cabal-install version 0.5.1 using version 1.4.0.1 of the library. On a mac there seem to be no problems, though. Am I doing something wrong? Thanks, Pedro