iPhone 5s slightly shorter than iPhone 5?

My understanding is that the two phones had the same dimensions, but immediately after putting my 5s in the case I had been using for my 5, I noticed that it shifter up and down in my case. Anyone else having this issue, or is it simply that my case has always been a little long but I didn't notice it (maybe the finish on the 5 kept it from sliding around noticeably)? The case is a Belkin grip candy sheer.