Hi, I'd expect the following program (compiled with ghc and without any specieal flags) to produce Just (Exited ExitSuccess) True but it produces Just (Exited ExitSuccess) False on Debian Lenny (ghc-6.8), OpenBSD-current (ghc-6.12.3), OpenBSD-current (ghc=7.0 from the 7.0 branch). module Main where import Data.IORef import System.Posix.Process import System.Posix.Signals import System.Posix.Unistd main = do caughtCHLD <- newIORef False installHandler sigCHLD (Catch $ writeIORef caughtCHLD True) Nothing pid <- forkProcess $ sleep 2 >> return () s <- sleep 8 getProcessStatus False False pid >>= print readIORef caughtCHLD >>= print The sigCHLD handler is never called in this program. Is this expected behaviour? If so, why? Ciao, Kili