Steps to reproduce: - Create a CSS3 horizontal box - Add two children with the same "flex-box" value and set their "box-sizing" CSS attribute to "border-box" - Add border and padding to the first one. The box's children should have the same width and "split" the box in half width but they don't. The first child expands unexpectedly.
Created attachment 124126 [details] Test case
box-flex hasn't been a part of the flexbox standard for over a year now.