Photo via Twitter

The rumors proved to be true on Friday night when Lollapalooza headliner Eminem brought out a special guest during his set.

A week ahead of their own joint tour, Rihanna joined the rapper on stage for a pair of their hits, "Love the Way You Lie" and "The Monster." The singer also teamed up with Em for "Stan," of which Dido provided vocals on the original 1999 track.

Bad Meets Evil and Slaughterhouse collaborator Royce da 5'9" also appeared during Eminem's set.

Watch clips below of fan footage.

(Updated with video of "Stan," via Pursuit of Dopeness)