diff --git a/QuickCheck.cabal b/QuickCheck.cabal
--- a/QuickCheck.cabal
+++ b/QuickCheck.cabal
@@ -1,5 +1,5 @@
 name:		QuickCheck
-version:	1.1.0.0
+version:	1.2.0.0
 license:	BSD3
 license-file:	LICENSE
 author:		Koen Classen and John Hughes
@@ -33,7 +33,7 @@
           Test.QuickCheck.Utils,
           Test.QuickCheck
   if flag(split-base)
-    build-depends:	base >= 3, random
+    build-depends:	base >= 3 && < 4, random
   else
     build-depends:	base < 3
   extensions:	CPP
diff --git a/Test/QuickCheck.hs b/Test/QuickCheck.hs
--- a/Test/QuickCheck.hs
+++ b/Test/QuickCheck.hs
@@ -96,9 +96,14 @@
 promote f = Gen (\n r -> \a -> let Gen m = f a in m n r)
 
 variant :: Int -> Gen a -> Gen a
-variant v (Gen m) = Gen (\n r -> m n (rands r !! (v+1)))
+variant v (Gen m) = Gen (\n r -> m n (rands r v))
  where
-  rands r0 = r1 : rands r2 where (r1, r2) = split r0
+  rands r0 0 = r0
+  rands r0 n = let (r1,r2) = split r0
+                   (n',s)  = n `quotRem` 2
+               in case s of
+                    0 -> rands r1 n'
+                    _ -> rands r2 n'
 
 generate :: Int -> StdGen -> Gen a -> a
 generate n rnd (Gen m) = m size rnd'
diff --git a/Test/QuickCheck/Batch.hs b/Test/QuickCheck/Batch.hs
--- a/Test/QuickCheck/Batch.hs
+++ b/Test/QuickCheck/Batch.hs
@@ -77,6 +77,10 @@
  -
  -}
 
+#if defined(__NHC__) && __NHC__ > 120
+#define BASE4 1
+#endif
+
 module Test.QuickCheck.Batch
    ( run		-- :: Testable a => a -> TestOptions -> IO TestResult
    , runTests		-- :: String -> TestOptions -> 
@@ -95,7 +99,11 @@
 import Control.Concurrent
 #endif
 import Control.Exception hiding (catch, evaluate)
+#if BASE4
+import qualified Control.Exception as Exception
+#else
 import qualified Control.Exception as Exception (catch, evaluate)
+#endif
 import Test.QuickCheck
 import System.IO.Unsafe
 
@@ -116,7 +124,11 @@
 data TestResult = TestOk 	String  Int [[String]]
 		| TestExausted 	String  Int [[String]]
 		| TestFailed   [String] Int
+#if BASE4
+		| TestAborted   SomeException
+#else
 		| TestAborted   Exception
+#endif
 
 tests :: Config -> Gen Result -> StdGen -> Int -> Int -> [[String]] 
       -> IO TestResult
@@ -163,7 +175,13 @@
 				  takeMVar ready
 				  throwTo me NonTermination
 				  return ())
+#if BASE4
+                              (\ e -> case e of
+                                  Exception.ThreadKilled -> return ()
+                                  _ -> throw e))
+#else
 			      (\ _ -> return ()))
+#endif
 	     -- Tell the watcher we are starting...
 	     putMVar ready ()
              -- This is cheating, because possibly some of the internal message
@@ -242,5 +260,10 @@
 isBottom a = unsafePerformIO (do
 	a' <- try (Exception.evaluate a)
 	case a' of
+#if BASE4
+           Left e -> let _ = e :: SomeException -- XXX Euch, want pattern sigs
+                     in return True
+#else
 	   Left _ -> return True
+#endif
 	   Right _ -> return False)
diff --git a/prologue.txt b/prologue.txt
new file mode 100644
--- /dev/null
+++ b/prologue.txt
@@ -0,0 +1,8 @@
+A library for testing Haskell programs automatically. The programmer provides a
+specification of the program, in the form of properties which functions should
+satisfy, and QuickCheck then tests that the properties hold in a large number of
+randomly generated cases. Specifications are expressed in Haskell, using
+combinators defined in the QuickCheck library. QuickCheck provides combinators
+to define properties, observe the distribution of test data, and define test
+data generators. For more information, please see:
+<http://www.math.chalmers.se/~rjmh/QuickCheck/>.