Stairs can be tricky. Just ask Justin Bieber!
"So I decided I was gonna fall down the stairs," Justin says in the clip. It then flashes to a close shot of his scratched-up, red neck. "And so I did! So that's exactly what I did!"
Unfortunately for the Biebs, he didn't time his tumble too well. He captioned his Insta-video, "#whyigottafallandcutmyneckbeforeaphotoshoot fun."
Fortunately, Selena Gomez's on-off love was able to pull it together for the cameras.
"Shooting with @adidasNEOLabel today," he tweeted. "Making them make longer shirts."
It's hard to believe J.B. would ever want to cover up those abs!