diff --git a/assert.cabal b/assert.cabal
--- a/assert.cabal
+++ b/assert.cabal
@@ -1,5 +1,5 @@
 name:           assert
-version:        0.0.1.0
+version:        0.0.1.1
 synopsis:       Helpers for Control.Exception.assert
 description:
     GHC supports compile-time toggling of run-time assertions via the
@@ -37,8 +37,8 @@
     type: exitcode-stdio-1.0
     hs-source-dirs: tests
     main-is: rewrite.hs
-    build-depends: assert, base, Cabal, directory, filepath,
-        system-posix-redirect >= 1.0.0.1
+    build-depends: assert, base, bytestring, Cabal, directory, filepath,
+        system-posix-redirect >= 1.1
     ghc-options: -Wall -fignore-asserts
 
 -- vim: et sw=4 ts=4 sts=4:
diff --git a/src/Control/Exception/Assert.hs b/src/Control/Exception/Assert.hs
--- a/src/Control/Exception/Assert.hs
+++ b/src/Control/Exception/Assert.hs
@@ -23,10 +23,10 @@
         AssertionFailed failure <- fromException se
         return (Arse failure)
 
--- | Generic helper for 'assert' that includes a descriptive message to the
--- 'AssertFailure' exception if thrown. Use this to build your own 'assert'
--- helpers, such as 'byOrd'. A rule is included which rewrites
--- 'assertMessage' to 'id' when compiling with @-fignore-asserts@.
+-- | Generic helper for 'assert' that maps 'AssertFailure' 'Exception's to
+-- 'Arse', adding a descriptive message along the way. Use this to build
+-- your own 'assert' helpers, such as 'byOrd'. A rule is included which
+-- rewrites 'assertMessage' to 'id' when compiling with @-fignore-asserts@.
 {-# INLINE [1] assertMessage #-}
 {-# RULES "assertMessage" forall name msg.
     assertMessage name msg (\x -> x) = id #-}
diff --git a/tests/rewrite.hs b/tests/rewrite.hs
--- a/tests/rewrite.hs
+++ b/tests/rewrite.hs
@@ -1,6 +1,9 @@
 import Prelude
+import Control.Exception (IOException, catch)
 import Control.Exception.Assert
 import Control.Monad
+import qualified Data.ByteString.Char8 as BS
+import Data.Monoid
 import Distribution.PackageDescription
 import Distribution.Simple
 import Distribution.Simple.LocalBuildInfo
@@ -19,13 +22,16 @@
 
 hook :: PackageDescription -> LocalBuildInfo -> UserHooks -> BuildFlags -> IO ()
 hook pd lbi uh bf = do
-    forM_ ["hi", "o"] $ \ suf -> removeFile $
-        buildDir lbi </> "rewrite" </> "rewrite-tmp" </> "Main" <.> suf
+    -- more reliable way to force a rebuild?
+    removeDirectoryRecursive (buildDir lbi </> "rewrite" </> "rewrite-tmp")
+        `catch` \ e -> return () `const` (e :: IOException)
+
+    -- some versions of GHC prints to stderr
     (err, (out, _)) <- redirectStderr . redirectStdout $
         buildHook simpleUserHooks pd lbi uh bf
-    let combined = err ++ out
-    unless ("Rule fired: assertMessage" `elem` lines combined) $ do
-        putStr combined
+    let combined = BS.lines err <> BS.lines out
+    unless (BS.pack "Rule fired: assertMessage" `elem` combined) $ do
+        mapM_ BS.putStrLn combined
         putStrLn "Rule NOT fired: assertMessage"
         exitWith (ExitFailure 1)