diff --git a/Data/ConfigManager.hs b/Data/ConfigManager.hs
--- a/Data/ConfigManager.hs
+++ b/Data/ConfigManager.hs
@@ -63,7 +63,7 @@
 -- | Lookup for the value associated to a name and return the default value if
 -- no binding exists with the given name.
 
-lookupDefault :: Read a => a -> Name -> Config -> a
+lookupDefault :: Configured a => a -> Name -> Config -> a
 lookupDefault defaultValue name config = foldl (flip const) defaultValue $ lookup name config
 
 -- $format
@@ -122,7 +122,7 @@
 -- >   , mailFrom :: String
 -- >   , currency :: String
 -- >   , expiration :: DiffTime
--- >   } deriving (Read, Eq, Show)
+-- >   } deriving (Eq, Show)
 -- >
 -- > getConfig :: IO (Either Text Conf)
 -- > getConfig =
diff --git a/config-manager.cabal b/config-manager.cabal
--- a/config-manager.cabal
+++ b/config-manager.cabal
@@ -1,5 +1,5 @@
 name:                  config-manager
-version:               0.2.0.0
+version:               0.3.0.0
 synopsis:              Configuration management
 description:
   A configuration management library which supports: