One of the last tasks I had on my project '59 is to get the backup lights working properly. Just discovered that they only work when the lights are on. Is that the way they are supposed to work?

If so, I'd guess that the designer's intent is to assist the driver in backing up at night, vs a warning/safety feature for other drivers.
If not supposed to work that way, I guess I'll have to trace the wiring back and find out why it is that way.
If by design, has anyone rewired to a 'on' circuit so that the light will work in reverse all the time??
thanks for any replies...