Yesterday, famed butt-haver Justin Bieber posted his Great White Ass on Instagram and today, noted nipple-freer Chrissy Teigen responded with a game theory-approved tit-for-tat strategy, uploading a picture of husband John Legend’s backside.

Given her unparalleled expertise with online nudity rules, however, Teigen obscured the most obscene part of the ass (the crack) with an Instagram-approved knee.

Who will be the next celebrity to join social media’s exclusive nude-rear club? Hard to say, but the smart money’s on somebody trying (and failing) to send a direct message.

[Image via Instagram]