[PAULUS libro trigensimo tertio ad edictum. ] §18.4.5.pret quidem sine exceptione quoque, nisi in contrarium actum sit.
[PAULUS, on the Edict, book 33.] And indeed, also without defense, unless a contrary agreement has been made.
sed si certae summae debitor dictus sit, in eam summam tenetur uenditor: si incertae et nihil debeat, quanti intersit emptoris.
But if the debtor was said to be of a certain sum, the seller is bound for that sum; if of an uncertain sum, and he owes nothing, he is bound for the amount of the buyer's interest.