diff --git a/process-extras.cabal b/process-extras.cabal
--- a/process-extras.cabal
+++ b/process-extras.cabal
@@ -1,5 +1,5 @@
 Name:               process-extras
-Version:            0.3.3.5
+Version:            0.3.3.6
 Synopsis:           Process extras
 Description:        Extra functionality for the Process library
                     <http://hackage.haskell.org/package/process>.
diff --git a/src/System/Process/Common.hs b/src/System/Process/Common.hs
--- a/src/System/Process/Common.hs
+++ b/src/System/Process/Common.hs
@@ -44,8 +44,10 @@
 #endif
 #endif
 
+#if !MIN_VERSION_deepseq(1,4,2)
 -- | This instance lets us use DeepSeq's force function on a stream of Chunks.
 instance NFData ExitCode
+#endif
 
 class ProcessMaker a where
     process :: a -> IO (Handle, Handle, Handle, ProcessHandle)