diff --git a/hack.cabal b/hack.cabal
--- a/hack.cabal
+++ b/hack.cabal
@@ -1,10 +1,12 @@
 Name:                 hack
-Version:              2009.10.30
+Version:              2012.2.6
 Build-type:           Simple
 Synopsis:             a Haskell Webserver Interface
 Description:
-        
+
     Hack: a Haskell Webserver Interface
+    .
+    2012.02.06 added FlexibleInstances to fix an error under ghc >=7.2
 
 License:              BSD3
 License-file:         LICENSE
@@ -20,5 +22,5 @@
   ghc-options: -Wall
   build-depends: base >= 3 && < 5, data-default >= 0.2, bytestring
   hs-source-dirs: src/
-  exposed-modules:  
+  exposed-modules:
                     Hack
diff --git a/src/Hack.hs b/src/Hack.hs
--- a/src/Hack.hs
+++ b/src/Hack.hs
@@ -1,84 +1,84 @@
-{-# LANGUAGE TypeSynonymInstances #-}
-
-module Hack where
-
-import Data.Default
-import System.IO
-import qualified Data.ByteString.Lazy as L
-import qualified Data.ByteString as B
-
-type Application = Env -> IO Response
-type Middleware  = Application -> Application
-
-data RequestMethod =
-     OPTIONS
-  |  GET
-  |  HEAD
-  |  POST
-  |  PUT
-  |  DELETE
-  |  TRACE
-  |  CONNECT
-  deriving (Show, Read, Eq)
-
-data Hack_UrlScheme = HTTP | HTTPS deriving (Show, Eq)
-
-type HackErrors = String -> IO ()
-
-instance Show HackErrors where
-  show _ = "Error Stream"
-
-data Env = Env 
-  {  requestMethod  :: RequestMethod
-  ,  scriptName     :: String
-  ,  pathInfo       :: String
-  ,  queryString    :: String
-  ,  serverName     :: String
-  ,  serverPort     :: Int
-  ,  http           :: [(String, String)]
-  ,  hackVersion    :: [Int]
-  ,  hackUrlScheme  :: Hack_UrlScheme
-  ,  hackInput      :: L.ByteString
-  ,  hackErrors     :: HackErrors
-  ,  hackHeaders    :: [(String, String)]
-  ,  hackCache      :: [(B.ByteString, B.ByteString)]
-  ,  remoteHost     :: String
-  }
-  deriving (Show)
-
-data Response = Response
-  {  status   :: Int
-  ,  headers  :: [(String, String)]
-  ,  body     :: L.ByteString
-  }
-  deriving (Show)
-
-instance Default RequestMethod where
-  def = GET
-
-instance Default Hack_UrlScheme where
-  def = HTTP
-
-instance Default Response where
-  def = Response def def L.empty
-
-instance Default Env where
-  def = Env {
-        requestMethod = def
-      , scriptName    = def
-      , pathInfo      = def
-      , queryString   = def
-      , serverName    = def
-      , serverPort    = def
-      , http          = def
-      , hackVersion   = currentVersion
-      , hackUrlScheme = def
-      , hackInput     = L.empty
-      , hackErrors    = defaultErrorStream
-      , hackHeaders   = def
-      , hackCache     = def
-      , remoteHost    = def
-      }
-    where
-      defaultErrorStream = (hPutStr stderr)
-      currentVersion = [2009, 10, 30]
+{-# LANGUAGE TypeSynonymInstances, FlexibleInstances  #-}
+
+module Hack where
+
+import Data.Default
+import System.IO
+import qualified Data.ByteString.Lazy as L
+import qualified Data.ByteString as B
+
+type Application = Env -> IO Response
+type Middleware  = Application -> Application
+
+data RequestMethod =
+     OPTIONS
+  |  GET
+  |  HEAD
+  |  POST
+  |  PUT
+  |  DELETE
+  |  TRACE
+  |  CONNECT
+  deriving (Show, Read, Eq)
+
+data Hack_UrlScheme = HTTP | HTTPS deriving (Show, Eq)
+
+type HackErrors = String -> IO ()
+
+instance Show HackErrors where
+  show _ = "Error Stream"
+
+data Env = Env 
+  {  requestMethod  :: RequestMethod
+  ,  scriptName     :: String
+  ,  pathInfo       :: String
+  ,  queryString    :: String
+  ,  serverName     :: String
+  ,  serverPort     :: Int
+  ,  http           :: [(String, String)]
+  ,  hackVersion    :: [Int]
+  ,  hackUrlScheme  :: Hack_UrlScheme
+  ,  hackInput      :: L.ByteString
+  ,  hackErrors     :: HackErrors
+  ,  hackHeaders    :: [(String, String)]
+  ,  hackCache      :: [(B.ByteString, B.ByteString)]
+  ,  remoteHost     :: String
+  }
+  deriving (Show)
+
+data Response = Response
+  {  status   :: Int
+  ,  headers  :: [(String, String)]
+  ,  body     :: L.ByteString
+  }
+  deriving (Show)
+
+instance Default RequestMethod where
+  def = GET
+
+instance Default Hack_UrlScheme where
+  def = HTTP
+
+instance Default Response where
+  def = Response def def L.empty
+
+instance Default Env where
+  def = Env {
+        requestMethod = def
+      , scriptName    = def
+      , pathInfo      = def
+      , queryString   = def
+      , serverName    = def
+      , serverPort    = def
+      , http          = def
+      , hackVersion   = currentVersion
+      , hackUrlScheme = def
+      , hackInput     = L.empty
+      , hackErrors    = defaultErrorStream
+      , hackHeaders   = def
+      , hackCache     = def
+      , remoteHost    = def
+      }
+    where
+      defaultErrorStream = (hPutStr stderr)
+      currentVersion = [2009, 10, 30]