diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -65,7 +65,7 @@
 What if we could apply aeson's `FromJSON` / `ToJSON` pattern to give us variable lookups that provide both key-lookup and parse failure information?
 Armed with the `GeneralizedNewTypeDeriving` extension we can derive instances of `Var` that will parse to and from an environment. The `Var` typeclass is simply:
 ```haskell
-class (Read a, Show a) => Var a where
+class Var a where
   toVar   :: a -> String
   fromVar :: String -> Maybe a
 ```
diff --git a/envy.cabal b/envy.cabal
--- a/envy.cabal
+++ b/envy.cabal
@@ -1,5 +1,5 @@
 name:                envy
-version:             0.3.0.2
+version:             0.3.1.2
 synopsis:            An environmentally friendly way to deal with environment variables
 license:             BSD3
 license-file:        LICENSE
diff --git a/src/System/Envy.hs b/src/System/Envy.hs
--- a/src/System/Envy.hs
+++ b/src/System/Envy.hs
@@ -48,13 +48,10 @@
 import qualified Data.ByteString.Char8 as B8
 import qualified Data.ByteString.Lazy.Char8 as BL8
 ------------------------------------------------------------------------------
-
-------------------------------------------------------------------------------
 -- | Parser
 newtype Parser a = Parser { runParser :: ExceptT String IO a }
   deriving ( Functor, Monad, Applicative, MonadError String
            , MonadIO, Alternative, MonadPlus )
-
 ------------------------------------------------------------------------------
 -- | Variable type, smart constructor for handling Env. Variables
 data EnvVar = EnvVar { getEnvVar :: (String, String) }
@@ -145,7 +142,7 @@
 
 ------------------------------------------------------------------------------
 -- | Class for converting to / from an environment variable
-class (Read a, Show a) => Var a where
+class Var a where
   toVar   :: a -> String
   fromVar :: String -> Maybe a