Reverse lights come on with blinkers?

Here is the problem. I guy I work with has a 1989 Dodge pickup. When he turns on his blinkers, either one, the white reverse lights come on too. This only happens when he has his headlights on though. Has anyone seen this before, or have any idea where the wires might be crossed?

i'm willing to bet that the wires are melted together near the transmission.