diff --git a/pipes-shell.cabal b/pipes-shell.cabal
--- a/pipes-shell.cabal
+++ b/pipes-shell.cabal
@@ -4,7 +4,7 @@
 -- The name of the package.
 name:                pipes-shell
 
-version:             0.1.2
+version:             0.1.3
 
 -- A short (one-line) description of the package.
 synopsis:             Create proper Pipes from System.Process
@@ -59,21 +59,21 @@
   -- other-extensions:
 
   -- Other library packages from which modules are imported.
-  build-depends:   base >=4.5 && <4.8,
-                   stm >=2.4 && <2.5,
-                   process >=1.2 && <1.3,
-                   pipes >= 4.0.1 && <5,
-                   pipes-safe >= 2.0.1 && <3,
-                   pipes-bytestring >= 1.0.1 && <3,
-                   text >= 0.11.3.0 && <1.2,
-                   bytestring >= 0.10.0.2 && <0.11,
-                   async >= 2.0.1.0 && <2.1,
-                   stm-chans >= 3.0.0 && <3.1
+  build-depends:   async >= 2.0.1.0 && <2.1
+                 , base >=4.5 && <4.8
+                 , bytestring >= 0.10.0.2 && <0.11
+                 , pipes >= 4.0.1 && <5
+                 , pipes-bytestring >= 1.0.1 && <3
+                 , pipes-safe >= 2.0.1 && <3
+                 , process >=1.2 && <1.3
+                 , stm >=2.4 && <2.5
+                 , stm-chans >= 3.0.0 && <3.1
+                 , text >= 0.11.3.0 && <1.2
 
   -- Directories containing source files.
   hs-source-dirs:      src
 
-  ghc-options:         -O2 -Wall
+  ghc-options:         -Wall -O2
 
   -- Base language which the package is written in.
   default-language:    Haskell2010
@@ -89,21 +89,22 @@
   -- other-extensions:
 
   -- Other library packages from which modules are imported.
-  build-depends:   base >=4.5 && <4.8,
-                   stm >=2.4 && <2.5,
-                   process >=1.2 && <1.3,
-                   pipes >= 4.0.1 && <5,
-                   pipes-safe >= 2.0.1 && <3,
-                   pipes-bytestring >= 1.0.1 && <3,
-                   text >= 0.11.3.0 && <1.2,
-                   bytestring >= 0.10.0.2 && <0.11,
-                   async >= 2.0.1.0 && <2.1,
-                   stm-chans >= 3.0.0 && <3.1,
-                   hspec >= 1.7.2.0 && <1.10
+  build-depends:   async >= 2.0.1.0 && <2.1
+                 , base >=4.5 && <4.8
+                 , bytestring >= 0.10.0.2 && <0.11
+                 , directory >= 1.2.1.0
+                 , hspec >= 1.12.1
+                 , pipes >= 4.0.1 && <5
+                 , pipes-bytestring >= 1.0.1 && <3
+                 , pipes-safe >= 2.0.1 && <3
+                 , process >=1.2 && <1.3
+                 , stm >=2.4 && <2.5
+                 , stm-chans >= 3.0.0 && <3.1
+                 , text >= 0.11.3.0 && <1.2
 
   -- Directories containing source files.
   hs-source-dirs:  src, test
 
   -- Base language which the package is written in.
   default-language:    Haskell2010
-  ghc-options:         -Wall -rtsopts
+  ghc-options:         -Wall -O2 -rtsopts
diff --git a/src/Pipes/Shell.hs b/src/Pipes/Shell.hs
--- a/src/Pipes/Shell.hs
+++ b/src/Pipes/Shell.hs
@@ -42,9 +42,10 @@
 import           Control.Concurrent             hiding (yield)
 import           Control.Concurrent.Async
 import           Control.Concurrent.STM
-import           Control.Concurrent.STM.TBMChan
+import           Control.Concurrent.STM.TMChan
 import qualified System.IO                      as IO
 import           System.Process
+import           Debug.Trace
 
 import qualified Data.ByteString                as BS
 
@@ -134,13 +135,13 @@
 -- >>> runShell $ yield (BSC.pack "aaa") >?> pipeCmdEnv Nothing "tr 'a' 'A'" >-> PBS.stdout
 -- AAA
 pipeCmdEnv :: MonadSafe m =>
-           Maybe [(String,String)] ->
-           String ->
-           Pipe (Maybe BS.ByteString) (Either BS.ByteString BS.ByteString) m ()
+    Maybe [(String,String)] ->
+    String ->
+    Pipe (Maybe BS.ByteString) (Either BS.ByteString BS.ByteString) m ()
 pipeCmdEnv env' cmdStr = bracket (aquirePipe env' cmdStr) releasePipe $
   \(stdin, stdout, stderr) -> do
 
-    chan <- liftIO $ newTBMChanIO 4
+    chan <- liftIO $ newTMChanIO
     _ <- liftIO . forkIO $
       handlesToChan stdout stderr chan
 
@@ -152,7 +153,7 @@
     case got of
       Nothing -> do
         liftIO $ IO.hClose stdin
-        fromTBMChan chan
+        fromTMChan chan
       Just val -> do
         liftIO $ BS.hPutStr stdin val
         yieldOne chan
@@ -160,24 +161,24 @@
 
   -- *try* to read one line from the chan and yield it.
   yieldOne chan = do
-    mLine <- liftIO $ atomically $ tryReadTBMChan chan
+    mLine <- liftIO $ atomically $ tryReadTMChan chan
     whenJust (join mLine)
       yield
 
-  -- fill the TBMChan from the stdout and stderr handles
+  -- fill the TMChan from the stdout and stderr handles
   -- the current implementation reads stderr and stdout async
   handlesToChan stdout stderr chan = do
-    out <- async $ toTBMChan chan $ do
+    out <- async $ toTMChan chan $ do
            PBS.fromHandle stdout >-> P.map Right
            liftIO $ IO.hClose stdout
 
-    err <- async $ toTBMChan chan $ do
+    err <- async $ toTMChan chan $ do
            PBS.fromHandle stderr >-> P.map Left
            liftIO $ IO.hClose stderr
 
     forM_ [out, err] wait
 
-    atomically $ closeTBMChan chan
+    atomically $ closeTMChan chan
 
 -- | Like 'pipeCmdEnv' but doesn't set enviorment varaibles
 pipeCmd :: MonadSafe m =>
@@ -284,16 +285,16 @@
 whenJust (Just x) action = action x
 whenJust Nothing _       = return ()
 
-fromTBMChan :: (MonadIO m) => TBMChan a -> Producer' a m ()
-fromTBMChan chan = do
-  msg <- liftIO $ atomically $ readTBMChan chan
+fromTMChan :: (MonadIO m) => TMChan a -> Producer' a m ()
+fromTMChan chan = do
+  msg <- liftIO $ atomically $ readTMChan chan
   whenJust msg $ \m -> do
     yield m
-    fromTBMChan chan
+    fromTMChan chan
 
-toTBMChan :: MonadIO m => TBMChan a -> Producer' a m () -> m ()
-toTBMChan chan prod = runEffect $
-  for prod (liftIO . atomically . writeTBMChan chan)
+toTMChan :: MonadIO m => TMChan a -> Producer' a m () -> m ()
+toTMChan chan prod = runEffect $
+  for prod (liftIO . atomically . writeTMChan chan)
 
 -- | Creates the pipe handles
 aquirePipe :: MonadIO m =>