Barcelona would reportedly have to pay the full £131m fee for Ousmane Dembele if they sell the winger before the end of his contract.
The 21-year-old has fallen back down the pecking order this season, scoring just once since mid-September having begun the campaign with five goals in his first six games.
Barcelona are understood to be considering cashing in on the youngster, but German newspaper Die Welt claims that doing so before his contract expires in 2022 would force them to pay Borussia Dortmund the full £131m.
The Spanish giants have already paid £105m of that sum - including £96m up front and £9m worth of add-ons for appearances and Champions League qualification - but £26m remains tied up in future clauses.
Barca would reportedly be forced to pay that to Dortmund if they sell the France international, which would in turn increase their asking price for the attacker.
Dembele, whose first season with Barcelona was devastated by injury, has scored 10 goals in 38 appearances for the club across all competitions.