No offense, but this is the thread that comes up when you google this problem. And there is
nothing more aggravating than googling a tech problem and finding a bunch of threads that ask the question and offer no answer. So I'm going to give an answer to any problem I know the answer to regardless of the age of the post.
Also I know this works in the current version of Calibre (v0.9.18) because I had this problem, found this thread, solved it on my own.