[Haskell-cafe] Compiler constraints in cabal

Hi, I have a library, hmatrix-static, on Hackage. Version 0.3 (the current version) compiles with ghc-6.12. Let's say I want to upgrade my library using new features in ghc-7.0, and then release these upgrades as version 0.4. Is there any way to state in my cabal file that this new version will no longer compile under ghc-6.12? The reason I would like to state this is so that a user with ghc-6.12 can do 'cabal install hmatrix-static' (or do a cabal install of a program depending on hmatrix-static) and see that cabal will install version 0.3 rather than attempt to install version 0.4 and fail. Thanks for your help. Reiner