[HOpenGL] Problems compiling with profiling enabled

[Yann Morvan]

I was trying to compile GLUT and HOpenGL with profiling on (I added 
"GhcLibWays    = p" in buid.mk).
When it goes back to building the profiling versions, it fails with:

Graphics/UI/GLUT/Callbacks/Registration.hs:64:
    Couldn't match `Maybe Window' against `Window'
    Expected type: Maybe Window
    Inferred type: Window
    In the third argument of `maybe', namely `win'
    In the result of a 'do' expression:
    maybe (error (func ++ ": no current window")) return win

Even though things worked fine for the non profiling build.
I don't understand why it would behave differently.
I am using version 6.3 of the fptools disribution, because it is at that 
time that I had to play around to get fragment programs working. Was 
there known issues with profiling HOpenGL at that time ? Has a lot 
happened since ?
Do I need to do more than set GhcLibWays ?

Thank you for your help,

    Yann Morvan