Yes you can use it. At such voltages an 1V difference isn't much (it would be dangerous at a lower voltage though, an extreme example would be a nominal voltage of 1V and you give it 2V instead, in this case it's the double and can very well damage the device).
I've personally used a Thinkpad T60 on 26V instead of 19V and never had any issues, same with my current Dell E6400, so an 1V difference is nothing compared to that.