diff --git a/netlib-ffi.cabal b/netlib-ffi.cabal
--- a/netlib-ffi.cabal
+++ b/netlib-ffi.cabal
@@ -1,5 +1,5 @@
 Name:             netlib-ffi
-Version:          0.0.1
+Version:          0.1
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann <haskell@henning-thielemann.de>
@@ -20,7 +20,7 @@
 Build-Type:       Simple
 
 Source-Repository this
-  Tag:         0.0.1
+  Tag:         0.1
   Type:        darcs
   Location:    http://hub.darcs.net/thielema/netlib-ffi/
 
diff --git a/src/Numeric/Netlib/Class.hs b/src/Numeric/Netlib/Class.hs
--- a/src/Numeric/Netlib/Class.hs
+++ b/src/Numeric/Netlib/Class.hs
@@ -1,21 +1,23 @@
 module Numeric.Netlib.Class where
 
+import Foreign.Storable.Complex ()
 import Foreign.Storable (Storable)
 
 import Data.Functor.Compose (Compose(Compose, getCompose))
 import Data.Complex (Complex)
 
+import qualified Prelude
 import Prelude (Float, Double, ($))
 
 
-class (Storable a) => Real a where
+class (Floating a, Prelude.RealFloat a) => Real a where
    switchReal :: f Float -> f Double -> f a
 
 instance Real Float where switchReal f _ = f
 instance Real Double where switchReal _ f = f
 
 
-class Floating a where
+class (Storable a, Prelude.Fractional a) => Floating a where
    switchFloating ::
       f Float -> f Double ->
       f (Complex Float) -> f (Complex Double) -> f a