The present invention relates to an arrangement for testing the tightness of a container (2), comprising a testing chamber (3), in which the container (2) which is to be tested can be arranged, also comprising a pressure-altering device (5), in order to alter a pressure in the testing chamber (3) relative to a pressure in the container (2), further comprising a differential-pressure sensor (4) for determining a pressure difference between a reference pressure in a reference chamber (6) and a pressure in the testing chamber (3), and additionally comprising a valve (7) having a closing element (70), a first sealing seat (71) and a second sealing seat (72), wherein the first sealing seat (71) comprises a first sealing element (11, 21) for sealing the reference chamber (6) in relation to an antechamber, and wherein the second sealing seat (72) comprises a second sealing element (12, 22) for sealing the testing chamber (3) in relation to the antechamber (8).