Hallo, Is this the intended behaviour? > (bit-set? 3 99) #f > (fxbit-set? 3 99) *** ERROR IN (console)@12.1 -- (Argument 2) Out of range (fxbit-set? 3 99) 1> ,d > (##fxbit-set? 3 99) #f Cheers, -- -alex @asandroq http://www.ventonegro.org/