The spec was updated (almost 1 year ago) to define properly the static position of the positioned grid items: https://drafts.csswg.org/css-grid-1/issues-wd-20150108#issue-1 But we didn't apply this change in our implementation. The specific wording from the spec (https://drafts.csswg.org/css-grid/#static-position): "The static position [CSS21] of an absolutely-positioned child of a grid container is determined as if it were the sole grid item in a grid area whose edges coincide with the padding edges of the grid container. However, if the grid container parent is also the generator of the absolutely positioned element’s containing block, instead use the grid area determined in §11.1 With a Grid Container as Containing Block." This was already fixed in Blink: https://codereview.chromium.org/1929483002