There exit dialogs that have button choices like [ok] [cancel], where by default one of them is preselected. When you hit return then, the selected button is being "pressed". In your case, you should have [done] preselected, so that when one presses return, it is like pressing [done]. Then it would be normal and proper.
I know, seems like a little thing, but it's kinda loud for a little thing. I would certainly have a look at it and correct it.
