Steps to reproduce: 1. Define a width/height on a flex 2. Insert an image in it 3. Observe how its aspect-ratio affects its final size https://jsfiddle.net/zcqst2pr/ https://jsfiddle.net/zcqst2pr/1/ Did this work before? N/A Does this work in other browsers? Yes Actual results: Images do not flex as they do in Edge, which has been deemed per-spec in this case (see below). Expected results: Aspect-ratio should be preserved, except if the image is to be sized bigger than its normal size ("grow" test case). If it is, the flexing that takes place as a second step will shrink the image to fit the container. The reason flexing is different is that flex-shrink is 1 by default and flex-grow is 0 by default. Flexing doesn't have to take the image aspect-ratio into consideration, but should also refuse to shrink further than the image intrinsic size. Please discuss this issue at https://github.com/w3c/csswg-drafts/issues/1112 if you disagree with the test results