diff --git a/ghc-mod.cabal b/ghc-mod.cabal
index e69b81a..b8b8028 100644
--- a/ghc-mod.cabal
+++ b/ghc-mod.cabal
@@ -147,6 +147,8 @@ Executable ghc-modi
                         Misc
                         Utils
   GHC-Options:          -Wall -threaded
+  if os(windows)
+      Cpp-Options:      -DWINDOWS
   Default-Extensions:   ConstraintKinds, FlexibleContexts
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
@@ -154,6 +156,7 @@ Executable ghc-modi
                       , containers
                       , directory
                       , filepath
+                      , process
                       , split
                       , time
                       , ghc
diff --git a/src/GHCModi.hs b/src/GHCModi.hs
index 3b84bf8..565be8b 100644
--- a/src/GHCModi.hs
+++ b/src/GHCModi.hs
@@ -87,6 +87,7 @@ run opt ref = flip E.catches handlers $ do
     let rootdir = cradleRootDir cradle0
 --        c = cradle0 { cradleCurrentDir = rootdir } TODO: ?????
     setCurrentDirectory rootdir
+    prepareAutogen
     -- Asynchronous db loading starts here.
     symdbreq <- newSymDbReq opt
     (res, _) <- runGhcModT opt $ getCurrentWorld >>= loop symdbreq ref
@@ -128,6 +129,7 @@ loop symdbreq ref world = do
     when changed $ do
         liftIO $ ungetCommand ref cmdArg
         E.throw Restart
+    liftIO $ prepareAutogen
     let (cmd,arg') = break (== ' ') cmdArg
         arg = dropWhile (== ' ') arg'
     (ret,ok) <- case cmd of
diff --git a/src/Misc.hs b/src/Misc.hs
index 0395447..d9c0894 100644
--- a/src/Misc.hs
+++ b/src/Misc.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveDataTypeable, CPP #-}
 
 module Misc (
     GHCModiError(..)
@@ -14,18 +14,25 @@ module Misc (
   , newSymDbReq
   , getDb
   , checkDb
+  , prepareAutogen
   ) where
 
 import Control.Applicative ((<$>))
+import Control.Concurrent (threadDelay)
 import Control.Concurrent.Async (Async, async, wait)
 import Control.Exception (Exception)
+import Control.Monad (unless)
 import CoreMonad (liftIO)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
+import Data.List (isPrefixOf)
 import Data.Time (UTCTime)
 import Data.Typeable (Typeable)
+import System.Directory (getModificationTime, doesDirectoryExist, getDirectoryContents)
+import System.Process
+import System.IO (openBinaryFile, IOMode(..))
+
 import Language.Haskell.GhcMod
 import Language.Haskell.GhcMod.Internal
-import System.Directory (getModificationTime)
 
 ----------------------------------------------------------------
 
@@ -107,3 +114,59 @@ checkDb (SymDbReq ref act) db = do
         hoistGhcModT =<< liftIO (wait req)
       else
         return db
+
+----------------------------------------------------------------
+
+build :: IO ProcessHandle
+build = do
+#ifdef WINDOWS
+    nul <- openBinaryFile "NUL" AppendMode
+#else
+    nul <- openBinaryFile "/dev/null" AppendMode
+#endif
+    (_, _, _, hdl) <- createProcess $ pro nul
+    return hdl
+ where
+   pro nul = CreateProcess {
+       cmdspec = RawCommand "cabal" ["build"]
+     , cwd = Nothing
+     , env = Nothing
+     , std_in = Inherit
+     , std_out = UseHandle nul
+     , std_err = UseHandle nul
+     , close_fds = False
+     , create_group = True
+     , delegate_ctlc = False
+     }
+
+autogen :: String
+autogen = "dist/build/autogen"
+
+isAutogenPrepared :: IO Bool
+isAutogenPrepared = do
+    exist <- doesDirectoryExist autogen
+    if exist then do
+        files <- filter ("." `isPrefixOf`) <$> getDirectoryContents autogen
+        if length files >= 2 then
+            return True
+          else
+            return False
+      else
+        return False
+
+watch :: Int -> ProcessHandle -> IO ()
+watch 0 _ = return ()
+watch n hdl = do
+    prepared <- isAutogenPrepared
+    if prepared then
+        interruptProcessGroupOf hdl
+      else do
+        threadDelay 100000
+        watch (n - 1) hdl
+
+prepareAutogen :: IO ()
+prepareAutogen = do
+    prepared <- isAutogenPrepared
+    unless prepared $ do
+        hdl <- build
+        watch 30 hdl