Benjamin Urdapilleta's late penalty saw Castres edge past Racing 92 with a 16-13 win in Champions Cup Pool Four.
The sides were locked at 6-6 at half-time after two penalties apiece from Urdapilleta and Maxime Machenaud before a try from Edwin Maka, which was converted by Machenaud, put Racing in front.
The visitors looked set to hold on for victory until Maama Vaipulu crossed for a converted score in the 73rd minute, before Urdapilleta slotted the crucial kick.
Racing missed two late penalty attempts through Antoine Gilbert and Teddy Iribaren as Castres held on for their first win in the competition.
