diff --git a/Shellish.hs b/Shellish.hs
--- a/Shellish.hs
+++ b/Shellish.hs
@@ -35,6 +35,7 @@
 
 import Prelude hiding ( catch, readFile )
 import Data.List( isInfixOf, (\\) )
+import Data.Char( isAlphaNum )
 import Data.Typeable
 import Data.IORef
 import Data.Maybe
@@ -184,11 +185,14 @@
 -- own. Use carefully.
 rm_rf :: FilePath -> ShIO ()
 rm_rf f = path f >>= \f' -> do
-  let deletable = Permissions True True True True
   whenM (test_d f) $ do
-    find f' >>= mapM (\file -> liftIO $ setPermissions file deletable `catchany` \_ -> return ())
+    find f' >>= mapM (\file -> liftIO $ fixPermissions file `catchany` \_ -> return ())
     liftIO $ removeDirectoryRecursive f'
   whenM (test_f f) $ rm_f f'
+  where fixPermissions file =
+          do permissions <- liftIO $ getPermissions file
+             let deletable = permissions { readable = True, writable = True, executable = True }
+             liftIO $ setPermissions file deletable
 
 -- | Remove a file. Does not fail if the file already is not there. Does fail
 -- if the file is not a file.
@@ -373,7 +377,8 @@
 withTmpDir :: (FilePath -> ShIO a) -> ShIO a
 withTmpDir act = do
   dir <- liftIO $ getTemporaryDirectory
-  (path, handle) <- liftIO $ openTempFile dir "tmp"
+  tid <- liftIO $ myThreadId
+  (path, handle) <- liftIO $ openTempFile dir ("tmp"++filter isAlphaNum (show tid))
   liftIO $ hClose handle -- required on windows
   rm_f path
   mkdir path
diff --git a/shellish.cabal b/shellish.cabal
--- a/shellish.cabal
+++ b/shellish.cabal
@@ -3,7 +3,7 @@
 -- The package version. See the Haskell package versioning policy
 -- (http://www.haskell.org/haskellwiki/Package_versioning_policy) for
 -- standards guiding when and how versions should be incremented.
-Version:     0.1.3
+Version:     0.1.4
 
 Synopsis:    shell-/perl- like (systems) programming in Haskell