diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -63,7 +63,7 @@
   - Lookups don't attempt to parse the returned type into something meaningful (everything is returned as a `String`)
 
 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:
+Armed with the `GeneralizedNewTypeDeriving` extension we can derive instances of `Var` that will parse to and from an environment variable. The `Var` typeclass is simply:
 ```haskell
 class Var a where
   toVar   :: a -> String
@@ -148,14 +148,14 @@
 -- This record corresponds to our environment, where the field names become the variable names, and the values the environment variable value
 data PGConfig = PGConfig {
     pgHost :: String -- "PG_HOST"
-  , pgHost :: Int    -- "PG_PORT"
+  , pgPort :: Int    -- "PG_PORT"
   } deriving (Generic, Show)
 
 -- Default configuration will be used for fields that could not be retrieved from the environment
 instance DefConfig PGConfig where
   defConfig = PGConfig "localhost" 5432
 
-instance FromEnv PGConfig 
+instance FromEnv PGConfig
 -- Generically creates instance for retrieving environment variables (PG_HOST, PG_PORT)
 
 main :: IO ()
@@ -191,5 +191,35 @@
 main :: IO ()
 main =
   print =<< decodeEnv :: IO (Either String PGConfig)
+ -- PGConfig { pgHost = "customUrl", pgPort = 5432 }
+```
+
+It's also possible to avoid typeclasses altogether using `runEnv` with `gFromEnvCustom`.
+
+```haskell
+{-# LANGUAGE DeriveGeneric #-}
+module Main where
+
+import System.Envy
+import GHC.Generics
+
+data PGConfig = PGConfig {
+    connectHost :: String -- "PG_HOST"
+  , connectPort :: Int    -- "PG_PORT"
+  } deriving (Generic, Show)
+
+-- Default PGConfig
+instance DefConfig PGConfig where
+  defConfig = PGConfig "localhost" 5432
+
+-- All fields will be converted to uppercase
+getPGEnv :: IO (Either String PGConfig)
+getPGEnv = runEnv $ gFromEnvCustom Option {
+                    dropPrefixCount = 7
+                  , customPrefix = "PG"
+		  }
+
+main :: IO ()
+main = print =<< getPGEnv
  -- PGConfig { pgHost = "customUrl", pgPort = 5432 }
 ```
diff --git a/envy.cabal b/envy.cabal
--- a/envy.cabal
+++ b/envy.cabal
@@ -1,5 +1,5 @@
 name:                envy
-version:             1.1.0.0
+version:             1.2.0.0
 synopsis:            An environmentally friendly way to deal with environment variables
 license:             BSD3
 license-file:        LICENSE
@@ -25,8 +25,8 @@
                       , containers   == 0.5.*
                       , mtl          == 2.2.*
                       , text         == 1.2.*
-                      , time         == 1.5.*
-                      , transformers == 0.4.*
+                      , time         >= 1.5 && < 1.7
+                      , transformers >= 0.4 && < 0.6
   default-language:     Haskell2010
 
 test-suite spec
@@ -34,16 +34,16 @@
     ghc-options:        -Wall
     hs-source-dirs:     tests
     main-is:            Main.hs
-    build-depends:      base                 >= 4.7 && < 5
-                      , bytestring           == 0.10.*
+    build-depends:      base
+                      , bytestring
                       , envy                 == 1.1.*
                       , hspec                == 2.2.*
-                      , mtl                  == 2.2.*
+                      , mtl
                       , quickcheck-instances == 0.3.*
                       , QuickCheck           == 2.8.*
-                      , text                 == 1.2.*
-                      , time                 == 1.5.*
-                      , transformers         == 0.4.*
+                      , text
+                      , time
+                      , transformers
     default-language:   Haskell2010
 
 
diff --git a/src/System/Envy.hs b/src/System/Envy.hs
--- a/src/System/Envy.hs
+++ b/src/System/Envy.hs
@@ -111,7 +111,7 @@
 ------------------------------------------------------------------------------
 -- | Environment variable getter
 getE
-  :: forall a . (Typeable a, Var a)
+  :: forall a . (Var a)
   => String
   -> Parser a
 getE k = do
@@ -126,7 +126,7 @@
 
 ------------------------------------------------------------------------------
 -- | Environment variable getter
-env :: forall a. (Typeable a, Var a)
+env :: forall a. (Var a)
     => String
     -> Parser a
 env = getE
@@ -134,7 +134,7 @@
 ------------------------------------------------------------------------------
 -- | Environment variable getter returning `Maybe`
 getEMaybe
-  :: forall a . (Typeable a, Var a)
+  :: forall a . (Var a)
   => String
   -> Parser (Maybe a)
 getEMaybe k = do
@@ -145,15 +145,14 @@
 
 ------------------------------------------------------------------------------
 -- | Environment variable getter returning `Maybe`
-envMaybe :: forall a. (Typeable a, Var a)
+envMaybe :: forall a. (Var a)
   => String
   -> Parser (Maybe a)
 envMaybe = getEMaybe
 
 ------------------------------------------------------------------------------
 -- | For use with (.:?) for providing default arguments
-(.!=) :: forall a. (Typeable a, Var a)
-  => Parser (Maybe a)
+(.!=) :: Parser (Maybe a)
   -> a
   -> Parser a
 (.!=) p x  = fmap (fromMaybe x) p
@@ -218,7 +217,7 @@
 
 ------------------------------------------------------------------------------
 -- | Construct a `Parser` from a `selName` and `DefConfig` record field
-instance (Selector s, Typeable a, Var a) => GFromEnv (S1 s (K1 i a)) where
+instance (Selector s, Var a) => GFromEnv (S1 s (K1 i a)) where
   gFromEnv m@(M1 (K1 def)) opts =
       M1 . K1 <$> envMaybe (toEnvName opts $ selName m) .!= def
     where
@@ -253,7 +252,7 @@
 
 ------------------------------------------------------------------------------
 -- | smart constructor, Environment creation helper
-makeEnv :: ToEnv a => [EnvVar] -> EnvList a
+makeEnv :: [EnvVar] -> EnvList a
 makeEnv = EnvList
 
 ------------------------------------------------------------------------------
@@ -312,7 +311,7 @@
 
 ------------------------------------------------------------------------------
 -- | Unset Environment from a `ToEnv` constrained type
-unsetEnvironment :: ToEnv a => EnvList a -> IO (Either String ())
+unsetEnvironment :: EnvList a -> IO (Either String ())
 unsetEnvironment (EnvList xs) = do
   result <- try $ mapM_ (unsetEnv . fst . getEnvVar) xs
   return $ case result of