Does the entry into Laos from China at the Mohan/Boten crossing have any extra fee besides the $30 visa-on-arrival fee?

I've done this crossing several times, at least once in this direction, but don't remember everything.

I have more than enough US dollars for the visa on arrival. But I only have $20 and $10 bills. (I also have some passport photos.)

Usually I have some $1 bills for just such border crossings because I know at several places there's fee, typically $1 for something or other, official or not.

I can't recall if the Lao-Chinese border is a place with the extra fee.