[Twenty Fourteen] Must crop header image since last update

Since updating to 3.9, I now must display a full 1260 x 240 header image. Before I uploaded a smaller header image and didn’t crop it, that had the look I wanted.

Now WordPress is forcing resizing and cropping if I want to display any header image at all. I could edit header.php in a child theme, but I’d rather find out what is forcing this resize and stop that.