runInteractiveProcess and buffering

It looks like my problem has to do with buffering, but I don't know how to solve it. main :: IO () main = do (inp,out,err,pid) <- runInteractiveProcess "aseqdump" ["-p", "72:0"] Nothing Nothing hSetBuffering out NoBuffering hGetBuffering out >>= print hGetLine out >>= putStrLn return () The data of 'out' seems to be buffered, because 'aseqdump' must produce many lines until even the first one is returned by 'hGetLine' and printed by 'putStrLn'. I tried to disable buffering for 'out' and indeed 'NoBuffering' is printed to the terminal, but the output from 'aseqdump' is still deferred.