[ULPIANUS libro quadragensimo octauo ad Sabinum. ] §45.1.36.prSi quis, cum aliter eum conuenisset obligari, aliter per machinationem obligatus est, erit quidem suptilitate iuris obstrictus, sed doli exceptione uti potest: quia enim per dolum obligatus est, competit ei exceptio.
[ULPIAN, in the forty-eighth book on Sabinus.] If anyone, although it had been agreed that he should be bound in one way, has been bound in another way through machination, he will indeed be bound by the subtlety of the law, but he can employ the defense of fraud: for because he was bound through fraud, the plea is available to him.
idem est et si nullus dolus intercessit stipulantis, sed ipsa res in se dolum habet: cum enim quis petat ex ea stipulatione, hoc ipso dolo facit, quod petit.
The same is true even if no fraud on the part of the stipulator intervened, but the transaction itself contains fraud in itself; for when anyone sues on the basis of that stipulation, by the very fact that he sues, he acts with fraud.