Paul Simon brought out The Grateful Dead’s Bob Weir during his closing set at the Outside Lands festival on Sunday night.

As the festival takes place in San Francisco, Simon prefaced the surprise appearance by reminiscing about his time in Haight-Ashbury in the ’60s. He then proceeded to welcome Weir onto the stage for a duet performance of Simon & Garfunkel’s “The Boxer.”

Watch the performance below.