Can you ride the bike to check? The conventional wisdom about frame size is often wrong.
I see a lot of people--probably most people these days--on frames that would have been thought too small 10 or 15 years ago. In my case (I'm 6'4"), a series of shops steered me to 60 or 62cm frames for years, because that's the largest they carried. When I tried a 65cm Atlantis from Rivendell a few years ago, I was instantly more comfortable than I've been on a bike since I was a kid. There's also a belief that smaller frames are lighter and stiffer, which is technically true but not as important as fit and comfort. For that reason, I'd be inclined at least to try the larger size.
An old guideline that nobody heeds anymore, but that isn't completely useless, is to set the saddle so your leg extension is right, then close your hand around the exposed part of the seatpost. Your fist should just about hide it. If you have way more post sticking out than your hand can cover, go up a size.
You might also check with another shop or two to see what they recommend. If there's general agreement, go with their advice.