Brighton came from behind to beat Chelsea and reach the fifth round of the FA Cup.
The Blues took a fortunate lead early on when Cole Palmer's volleyed cross from the left was fumbled into his own net by Bart Verbruggen.
But Albion came back and Georginio Rutter headed in from Joel Veltman's cross.
And they took the lead when Rutter picked out Kaoru Mitoma - the subject of a rejected £54m bid from Saudi Arabian side Al-Nassr before the transfer deadline - who dinked the ball over Robert Sanchez.
Chelsea felt the goal should have been disallowed, as the ball struck Tariq Lamptey's arm in the build-up, though there are no video assistant referees in the FA Cup fourth round.
Those goals came from Albion's only shots in the first 60 minutes.
Enzo Maresca's visitors - who fielded a strong side - rarely looked like equalising, with Enzo Fernandez shooting over the bar, and have now gone five away games without victory.
The clubs meet again at Brighton's Amex Stadium on Friday (20:00 GMT) in the Premier League, where Chelsea are nine points and six places above their cup conquerors.