[HOpenGL] clear [ColorBuffer]

Hello, The program: import Graphics.Rendering.OpenGL import Graphics.UI.GLUT main = do _ <- getArgsAndInitialize createWindow "Hello World" displayCallback $= clear [ ColorBuffer ] mainLoop and the problem: The ColorBuffer is not cleared, the window shows what was there before it was created. Creating windows, drawing points,... works all well, but "clear [ ColorBuffer ]" seems not to work. (I'm using the ghc 6.6 on Windows) Thanks in advance for your help.