[Haskell-cafe] Problems on installing sizes-types package

Hello to all! I'm trying to install the sized-types package, a dependency for kansas lava: http://hackage.haskell.org/package/sized-types using cabal, and the following error message is returned: Data/Sized/Sparse/Matrix.hs:61:26: Could not deduce (Eq a) arising from a use of `prune' from the context (Size m, Size n, Size m', Size n', n ~ m', Num a) bound by the type signature for mm :: (Size m, Size n, Size m', Size n', n ~ m', Num a) => Matrix (m, n) a -> Matrix (m', n') a -> Matrix (m, n') a at Data/Sized/Sparse/Matrix.hs:50:7-112 Is it a known issue? Is there some way to solve it? I'm using GHC 7.6.3 and plataform 2013.2.0.0. Best, Rodrigo