On the surface, the iPhone XS looks exactly like an iPhone X. Same dual-camera arrangement in the back, same general TrueDepth camera setup on the front, same display styling. So, if you’re looking for a case to fit on that iPhone XS, you may think of saving a few dollars by buying an iPhone X case — just as former iPhone 5s owners were able to reuse their cases when upgrading to the iPhone SE.

Wrong. At least that’s what Macotakara found when taking a caliper to the old cases and new phones. For one, the iPhone XS dual-camera module on the rear side is about 0.4mm wider than the one found on the iPhone X. It has also moved slightly.

Even though the phones themselves have the same dimensions, this means that putting an iPhone X in an iPhone XS will leave a gap between the case opening and the camera modules while an iPhone XS in an iPhone X may not fit without some finagling.

The outlet also surmised that the Hall sensor may have been placed in a different location as the iPhone X does not turn on when the cover on the iPhone XS Leather folio is flipped open.

Apple has different specific guidelines for accessories makers when it comes to cases for the iPhone X and iPhone XS. Furthermore, iPhone XS cases listed on the Apple Online Store do not specify compatibility with the iPhone X.