diff --git a/Control/Concurrent/Thread/Group.hs b/Control/Concurrent/Thread/Group.hs
--- a/Control/Concurrent/Thread/Group.hs
+++ b/Control/Concurrent/Thread/Group.hs
@@ -75,7 +75,7 @@
 -- from threads:
 import Control.Concurrent.Thread        ( Result )
 import Control.Concurrent.Raw           ( rawForkIO, rawForkOn )
-#ifdef __HADDOCK__
+#ifdef __HADDOCK_VERSION__
 import qualified Control.Concurrent.Thread as Thread ( forkIO
                                                      , forkOS
                                                      , forkOn
diff --git a/Setup.hs b/Setup.hs
deleted file mode 100644
--- a/Setup.hs
+++ /dev/null
@@ -1,45 +0,0 @@
-#! /usr/bin/env runhaskell
-
-{-# LANGUAGE NoImplicitPrelude, UnicodeSyntax #-}
-
-module Main (main) where
-
-
--------------------------------------------------------------------------------
--- Imports
--------------------------------------------------------------------------------
-
--- from base
-import System.IO ( IO )
-
--- from cabal
-import Distribution.Simple ( defaultMainWithHooks
-                           , simpleUserHooks
-                           , UserHooks(haddockHook)
-                           , Args
-                           )
-
-import Distribution.Simple.LocalBuildInfo ( LocalBuildInfo(..) )
-import Distribution.Simple.Program        ( userSpecifyArgs )
-import Distribution.Simple.Setup          ( HaddockFlags )
-import Distribution.PackageDescription    ( PackageDescription(..) )
-
-
--------------------------------------------------------------------------------
--- Cabal setup program which sets the CPP define '__HADDOCK __' when haddock is run.
--------------------------------------------------------------------------------
-
-main ∷ IO ()
-main = defaultMainWithHooks hooks
-  where
-    hooks = simpleUserHooks { haddockHook = haddockHook' }
-
--- Define __HADDOCK__ for CPP when running haddock.
-haddockHook' ∷ PackageDescription → LocalBuildInfo → UserHooks → HaddockFlags → IO ()
-haddockHook' pkg lbi =
-  haddockHook simpleUserHooks pkg (lbi { withPrograms = p })
-  where
-    p = userSpecifyArgs "haddock" ["--optghc=-D__HADDOCK__"] (withPrograms lbi)
-
-
--- The End ---------------------------------------------------------------------
diff --git a/threads.cabal b/threads.cabal
--- a/threads.cabal
+++ b/threads.cabal
@@ -1,7 +1,7 @@
 name:          threads
-version:       0.5.1.7
-cabal-version: >= 1.9.2
-build-type:    Custom
+version:       0.5.1.8
+cabal-version: 1.20
+build-type:    Simple
 stability:     experimental
 author:        Bas van Dijk <v.dijk.bas@gmail.com>
                Roel van Dijk <vandijk.roel@gmail.com>
@@ -50,9 +50,6 @@
 source-repository head
   Type: git
   Location: git://github.com/basvandijk/threads.git
-
-custom-setup
-    setup-depends: base >= 4.4 && < 5, Cabal >= 1.12 && < 3.9
 
 -------------------------------------------------------------------------------