On Wednesday, Justin Bieber wrapped up a three-night, sold-out residency at L.A.’s Staples Center for his Purpose World Tour, where pretty much everyone who’s anyone caught a glimpse of the action. His No. 1 fan, Kanye West? Check. A blonde-wigged Kylie Jenner? Check. Big Sean? Check. Even Bieber’s ex Selena Gomez? Yep, check.

Among the most enthusiastic of celebrity guests, however, were 5 Seconds of Summer bandmates Ashton Irwin and Calum Hood, who couldn’t resist catchy Bieber’s rainy spectacle. And lest you think they’re only casual “fans” who just showed up for a free night out, the two Aussies proved they’re bonafide Beliebers at heart by sharing a vid of them jamming out to “Baby.”

OK, true, you’d be hard-pressed to find anyone in the world who can’t sing the “Baby” chorus off the top of their head (“Baby, baby, baby, ooooh” isn’t exactly a brain-bender), but dammit, Ash and Cal sang it with feeling. Sounds good, feels good.