Dog peeing when company came over?

It wasn't when they went to pet him it was when we weren't looking, just when everyone was talking, one time it was right in front of us in the living room! There were 6 people total. We rescued him 6 months ago and he is 10 years old, a pomeranian and never has accidents in the house or submissive urination. Could it be that he was trying to get attention, or more like too excited...he knows to bark at the door when he needs to go out, so I think he was doing it for attention...any thoughts on how I can prevent it from happening again?