Sofia Richie In Bieber's Pants

9/2/2016 7:01 AM PDT

Sofia Richie -- In Bieber's Pants (PHOTO)

Sofia Richie doesn't need to wear Justin Bieber's shirts to prove they're a thing ... she just rocks his pants instead. 

JB's gf was out in WeHo Thursday rocking a cropped top and official Purpose Tour sweatpants.

Even without Justin, Sofia's still reppin' her boo. Keeper material?