diff --git a/src/Test/Framework/Providers/Sandbox.hs b/src/Test/Framework/Providers/Sandbox.hs
--- a/src/Test/Framework/Providers/Sandbox.hs
+++ b/src/Test/Framework/Providers/Sandbox.hs
@@ -26,11 +26,6 @@
 import Control.Exception.Lifted
 import Control.Monad hiding (fail)
 import Control.Monad.Reader (ask)
-import Control.Monad.Trans.Error (runErrorT)
-import Control.Monad.Trans.Reader (runReaderT)
-import Data.Either
-import Prelude hiding (error, fail)
-import qualified Prelude (error)
 import System.Console.ANSI
 import System.Environment
 import System.Exit
@@ -55,9 +50,9 @@
       if isExcluded options name then return $ Test name (SandboxTest Skipped)
         else withSystemTempDirectory (name ++ "_") $ \dir -> do
                env <- newSandboxState name dir
-               result <- (runReaderT . runErrorT . runSandbox) (putOptions options >> sandboxTestGroup name tests `finally` stopAll) env
+               result <- runSandbox (putOptions options >> sandboxTestGroup name tests `finally` stopAll) env
                case result of
-                 Left error -> return $ Test name (SandboxTest (Failure error))
+                 Left error' -> return $ Test name (SandboxTest (Failure error'))
                  Right x -> return x
   ]
 
@@ -88,10 +83,10 @@
 sandboxTest name test = withTest name $ do
   res <- do
     ref <- ask
-    liftIO $ flip (runReaderT . runErrorT . runSandbox) ref $ test `catches` handlers
+    liftIO $ flip runSandbox ref $ test `catches` handlers
   liftIO $ printTestResult res
   case res of
-    Left error -> return $ Test name (SandboxTest (Failure error))
+    Left error' -> return $ Test name (SandboxTest (Failure error'))
     Right _ -> return $ Test name (SandboxTest Passed)
   where handlers = [ Handler exitHandler
                    , Handler interruptHandler
@@ -110,7 +105,7 @@
 yieldProgress p = do
   pl <- getVariable prettyPrintVariable []
   unless (null pl) $ liftIO $ putStr " / "
-  setVariable prettyPrintVariable (p : pl)
+  _ <- setVariable prettyPrintVariable (p : pl)
   liftIO $ putStrColor Dull Blue p >> hFlush stdout
 
 ----------------------------------------------------------------------
diff --git a/src/Test/Framework/Providers/Sandbox/Internals.hs b/src/Test/Framework/Providers/Sandbox/Internals.hs
--- a/src/Test/Framework/Providers/Sandbox/Internals.hs
+++ b/src/Test/Framework/Providers/Sandbox/Internals.hs
@@ -10,10 +10,7 @@
 
 import Control.Concurrent
 import Control.Monad hiding (fail)
-import Data.Either
 import Data.Typeable
-import Prelude hiding (error, fail)
-import qualified Prelude (error)
 import System.Console.ANSI
 import System.IO
 
@@ -53,14 +50,14 @@
 instance Testlike SandboxTestRunning SandboxTestResult SandboxTest where
   testTypeName _ = "Sandbox tests"
   runTest _ (SandboxTest res) = runImprovingIO $ return res
-  runTest _ (SandboxCleaning mvar) = runImprovingIO $ do TF.liftIO $ takeMVar mvar
+  runTest _ (SandboxCleaning mvar) = runImprovingIO $ do _ <- TF.liftIO $ takeMVar mvar -- ToDo: Why this return-value is dicarded?
                                                          return Passed
 
 withTest :: String -> Sandbox b -> Sandbox b
 withTest name action = withVariable testVariable name $
   bracket (do level <- getVariable testLevelVariable 0
               liftIO $ printTestName level name
-              setVariable testLevelVariable $! level + 1
+              _ <- setVariable testLevelVariable $! level + 1
               return level)
           (setVariable testLevelVariable)
           (const action)
@@ -84,7 +81,7 @@
 printTestResult :: Either String a -> IO ()
 printTestResult r =
   case r of
-    Left error -> putStr " [" >> putStrColor Vivid Red "Fail" >> putStrLn ("] " ++ error)
+    Left error' -> putStr " [" >> putStrColor Vivid Red "Fail" >> putStrLn ("] " ++ error')
     _ -> putStr " [" >> putStrColor Vivid Green "OK" >> putStrLn "]"
 
 putStrColor :: ColorIntensity -> Color -> String -> IO ()
diff --git a/test-framework-sandbox.cabal b/test-framework-sandbox.cabal
--- a/test-framework-sandbox.cabal
+++ b/test-framework-sandbox.cabal
@@ -1,5 +1,5 @@
 Name:           test-framework-sandbox
-Version:        0.0.2.3
+Version:        0.0.2.4
 Cabal-Version:  >= 1.14
 Category:       Testing
 Synopsis:       test-sandbox support for the test-framework package
@@ -13,7 +13,7 @@
                 <http://gree.github.io/haskell-test-sandbox/>
                 .
                 A full example project is available at:
-                <https://git.gree-dev.net/benjamin-surma/flare-tests/>
+                <https://git.github.com/benjamin-surma/flare-tests/>
                 .
                 Extensive documentation is available in the source code itself.
 License:        BSD3
@@ -29,16 +29,18 @@
 Source-Repository this
     Type:       git
     Location:   https://github.com/gree/haskell-test-sandbox
-    Tag:        test-framework-sandbox_0.0.2.3
+    Tag:        test-framework-sandbox_0.0.2.4
 
 Library
     Exposed-modules:    Test.Framework.Providers.Sandbox
                         Test.Framework.Providers.Sandbox.Internals
 
     Build-Depends:      base >=4 && <5, ansi-terminal, lifted-base, mtl,
-                        temporary, test-framework >=0.8.0.3, test-sandbox >=0.0.1.5 && <0.0.2,
+                        temporary, test-framework >=0.8.0.3, test-sandbox >=0.0.1.9 && <0.0.2,
                         transformers
 
     Hs-source-dirs:     src
 
     Default-Language:   Haskell2010
+
+    ghc-options:       -Wall