Ween’s headlining set at Chicago’s North Coast Music Festival last night found them collaborating with Primus’ Les Claypool on “The Mollusk” about halfway through the band’s set. Watch the performance above.

Claypool’s affiliation with Ween goes back a number of years as Dean Ween was a regular guest with Claypool’s Duo de Twang (the two even have fishing videos together) as well as the Claypool Lennon Delirium. Claypool has also covered “The Mollusk,” the same song he did last night, with The Dean Ween Group in year’s past.

Next up for Ween is a late September run at San Francisco with a two-night run at The Masonic.