Hello, I discovered a bug in our: Control.Concurrent.Thread In the documentation of 'forkIO' we specify that the forked thread inherits the blocked state of its parent. However our implementation did not ensure this. The newly released concurrent-extra-0.3.1 fixes this. This release also adds the following function: -- |Like 'wait' but will rethrow the exception that was thrown in target thread. unsafeWait ∷ ThreadId α → IO α unsafeWait tid = wait tid >>= either (\(SomeException e) → throwIO e) return Documentation: http://hackage.haskell.org/package/concurrent-extra-0.3.1 To install this latest release do: cabal update cabal install concurrent-extra Or get the development sources using: darcs get http://code.haskell.org/concurrent-extra regards, Bas