Toulon president Mourad Boudjellal has expressed his concern at the decision to select Nigel Owens to referee the Champions Cup final.
The Welsh official will take charge of his fourth European final, having previously overseen the 2008, 2009 and 2012 finals.
However Boudjellal, who last year made a special request to avoid Owens in Toulon's quarter-final against Leinster, believes the Welshman might favour Clermont at Twickenham.
Last year Owens controversially sin-binned Brock James and awarded a penalty try to Saracens in their 46-6 semi-final win over Clermont.
Boudjellal fears that Owens might subconsciously try to make up for that decision, while also taking the chance to again play down his side's chances, regardless of who is refereeing.
Asked if he was worried about the refereeing in the final, Boudjellal told RMC: "When his name is Nigel Owens, yes! He's a very controversial referee.
"I think he has a debt towards Clermont because against Saracens last year, he didn't always make the right decisions.
"I hope he won't try to make up for that. But Nigel Owens won't be needed to beat us."