Hello glasgow-haskell-users, i've looked for this bug in Trac but don't found anything. so: startGUI action = runInBoundThread $ do unsafeInitGUIForThreadedRTS myThreadId >>= writeIORef guiThread action >>= widgetShowAll mainGUI guiThread = unsafePerformIO$ newIORef$ error "undefined GUI::guiThread" Later in the same thread i ask for myThreadId and get different value. interesting that value returned in startGUI is 23 while later values are about 7000. probably this reflects total amount of threads created so far so that's the problem. Win API call returns constant thread number (that looks natural since the thread is bound). so either: 1) it's feature - please mention this in docs 2) it was fixed since 6.6.1 3) we need full-scale bugreport using 6.10.2 -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com