Paris - An added-time try stopped South Africa's Rugby World Cup winner Cheslin Kolbe from marking his first career appearance at flyhalf with a win as Toulouse lost 30-27 at Racing 92 in the French Top 14 on Sunday.
Olivier Klemenczak scored 110 seconds into additional time to lift Racing to third.
Kolbe, usually a winger, kicked 10 points for the champions.
"It hurts going down in the last minute. We had the game in the bag. It's really disappointing," Kolbe said.
"I haven't been at flyhalf for a very long time. It's a different game, it's a different way of thinking about how you have to manage a game by giving the calls for the lineouts and the scrums."
Both sides had five players unavailable due to their France commitment including the visitors' in-form half-back pair of Antoine Dupont and Romain Ntamack.
But Scotland's Finn Russell played his first Racing game since missing the first two rounds of the Six Nations for disciplinary and personal reasons.
Klemenczak's late effort followed tries by Fabien Sanconnie and Olivier Laborde's for the Parisians.
Former New Zealand under-20 centre Pita Ahki opened the scoring for Toulouse on 13 minutes with his third try of the campaign after the hosts dominated the early territory. Sebastien Bezy converted.
Experienced scrum-half Maxime Machenaud, making just his fourth start of the season, cut the deficit to 7-3 three minutes later.
Racing took the lead for the first time as Sanconnie scored off the back of a rolling maul and Machenaud's conversion made it 10-7 after 25 minutes.
Lucas Tauzin's touchline diving try after half an hour and Kolbe's following conversion took the hosts back into the lead.
Kolbe kicked the first penalty of his senior career five minutes later before the hosts equalised 72 seconds into added time at the end of the first half.
Russell found Ben Volavola who fed replacement centre Dorian Laborde with a basketball pass to cross in the corner.
Machenaud added the extras from the touchline and the sides were level 17-17 at the break.
Machenaud put his side back in the lead with his second penalty before Toulouse reclaimed their hold on the match.
Sofiane Guitoune intercepted Russell's pass on his own 22-metre line and the centre, who featured for France at last year's World Cup ran in unopposed under the posts for a 24-22 lead with half an hour to play after Kolbe's conversion.
Kolbe stretched the Toulouse lead to 27-20 with a quarter of the game to go with a mammoth 47-metre penalty.
Teddy Iribaren replaced Machenaud and made it 27-23 with eight minutes to play with a three-pointer from in front of the posts.
Kolbe made his first error from the tee with three minutes to play, missing a penalty.
Then Klemenczak dived over in the corner for the winning score.
Earlier on Sunday, Fiji wing Filipo Nakosi scored his first try of the season as Castres beat bottom-side Agen 43-24 to move up to 10th place.
On Saturday Nakosi's fellow countryman Semi Radradra dotted down twice as Bordeaux-Begles leapfrogged Lyon to the top of the table with a 37-19 win at a sold-out Stade Chaban-Delmas.