No reverse lights?

I live in Germany and I am trying to get my recently purchased 99 TJ registered. It has an auxiliary reverse light mounted to the bumper, but there seems to be no other place on the car to have reverse lights. The tail light assembly has a turn signal, brake lights and tail lights, but no place for reverse lights. The previous owner made some questionable "upgrades", but if this is part of that mess, I don't even know how to fix it. How do the reverse lights on TJs normally work?