Barcelona are counting on Nice selling Jean-Clair Todibo in the coming week.
The French defender is a target for Manchester United.
And should a deal go through, Barca will be due a 20 per cent cut of the transfer fee from the sale.
Barca negotiated the clause when selling Todibo to Nice.
United are said to be willing to pay 30m to sign the centre-half before next week's transfer deadline.