1996 VW Gulf GTI ABS Light

I just installed a new rear caliper on my son's 1996 VW Gulf GTI. The install went flawlessly with very minor fluid loss. I placed saran wrap under the filler cap to limit this even further. The bleeding process went easily with only five cycles needed to eliminate the air. I have a very firm pedal at this point BUT the ABS light has come on. I went over the system to insure that there are no leaks and it is as dry as a bone. Does anybody have any hints on what might be causing the problem and how to reset the ABS indicator light.