Is a bicycle frame with a dent in the top cross bar still safe to ride?

I am shopping for a reasonably-priced touring bike for some short rides – 1–3 days – and found one for sale with a small dent. It is a steel frame, not aluminum, so I am wondering if it is still sound. I haven’t seen it in person yet, but I am guessing it is at least a couple mm deep, on the side of the top cross bar.