The Drivers' Championship was decided in controversial circumstances at the penultimate race of the season in Japan, when Prost and teammate Ayrton Senna, who needed to win the race, collided in the closing laps. Prost retired while Senna rejoined the track after a push start and crossed the line first, only to be disqualified for not rejoining the track correctly. This handed Prost the title, his last with McLaren before joining Ferrari for 1990.