They had dance routines and everything. Such pros.
Mrs Carter made the surprise appearance at the Coachella Valley Arts and Music Festival on Saturday night, when she joined her younger sis onstage as she performed her hit Losing You.
27-year-old Solange is a regular at the annual three-day festival and also performed the same track last year with The XX, wouldn't you know.
Meanwhile, Jay Z also shocked fans by jumping on stage to perform an impromptu rendition of Dead Presidents II during his friend Nas's midnight set.
The 44-year-old rapper then rapped Where I'm From, before Nas, 40, continued with his show, which honoured the 20th anniversary of his debut album 'Illmatic.' P Diddy then helped him end his set by stopping by to perform Hate Me Now.
Meanwhile, Katy Perry and Robert Pattinson were getting on down at the H&M Loves Music soiree. More on that here.