Rear (tailgate) dome light will not turn off

The rear/tailgate dome light will not turn off. Earlier in the day I was working on the actuators on the SUV, on passenger side front and in the back tailgate. I did not notice the light on then, but it was sunny out. When I returned to my SUV tonight to drive home, I did not notice the light on then either. I think I would have seen it on. However, when I started the car I then noticed the light on in the back. I do not ever remember seeing that light on before. I got out and tried to find a button or switch to turn it off, to no avail. I drove home with it on, and had no idea what to do about it. I am sure my battery will be drained in the morning. :( Any idea on how to fix this problem?