diff --git a/Data/Pool.hs b/Data/Pool.hs
--- a/Data/Pool.hs
+++ b/Data/Pool.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE PackageImports #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE RankNTypes #-}
 module Data.Pool
     ( -- * Using pools
       createPool
@@ -87,8 +89,15 @@
         Just x' -> return x'
         Nothing -> I.liftIOOp (bracket (poolMake p) (poolFree p)) f
 
+mask :: I.MonadControlIO m => ((forall a. m a -> m a) -> m b) -> m b
+#if MIN_VERSION_base(4,3,0)
+mask = I.mask
+#else
+mask f = I.block $ f I.unblock
+#endif
+
 withPool :: I.MonadControlIO m => Pool a -> (a -> m b) -> m (Maybe b)
-withPool p f = I.mask $ \unmask -> do
+withPool p f = mask $ \unmask -> do
     eres <- liftIO $ atomicModifyIORef (poolData p) $ \pd ->
         case poolAvail pd of
             x:xs -> (pd { poolAvail = xs }, Right x)
diff --git a/pool.cabal b/pool.cabal
--- a/pool.cabal
+++ b/pool.cabal
@@ -1,5 +1,5 @@
 name:            pool
-version:         0.1.0.1
+version:         0.1.0.2
 license:         BSD3
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>