diff --git a/test/Data/Conduit/Process/UnixSpec.hs b/test/Data/Conduit/Process/UnixSpec.hs
--- a/test/Data/Conduit/Process/UnixSpec.hs
+++ b/test/Data/Conduit/Process/UnixSpec.hs
@@ -13,17 +13,17 @@
 import Control.Monad.Trans.Class (lift)
 import Control.Concurrent (threadDelay)
 import System.Posix.Signals (sigKILL, sigTERM)
+import qualified Control.Concurrent.MVar as M
 
 iorefSink :: IO (Sink ByteString IO (), IO L.ByteString)
 iorefSink = do
-    ref <- I.newIORef id
-    let sink = CL.mapM_ $ \bs -> do
-            !() <- I.atomicModifyIORef ref $ \front -> (front . (bs:), ())
-            return ()
-        getLBS = do
-            front <- I.readIORef ref
-            return $ L.fromChunks $ front []
-    return (sink, getLBS)
+    m <- M.newEmptyMVar
+    let sink front = do
+            mbs <- await
+            case mbs of
+                Nothing -> lift $ M.putMVar m $ L.fromChunks $ front []
+                Just bs -> sink $ front . (bs:)
+    return (sink id, M.takeMVar m)
 
 spec :: Spec
 spec = describe "unix-process-conduit" $ do
diff --git a/unix-process-conduit.cabal b/unix-process-conduit.cabal
--- a/unix-process-conduit.cabal
+++ b/unix-process-conduit.cabal
@@ -2,7 +2,7 @@
 --  documentation, see http://haskell.org/cabal/users-guide/
 
 name:                unix-process-conduit
-version:             0.2.0.1
+version:             0.2.0.2
 synopsis:            Run processes on Unix systems, with a conduit interface
 description:         This library allows you to provide @conduit@ datatypes for the input and output streams. Note that you must compile your programs with @-threaded@.
 homepage:            https://github.com/snoyberg/conduit