A first element (100) of the quick connector (R) comprises a piston (130) equipped with a valve (150) for selectively closing off an inner duct (C100) of said first element (100). The piston is movable, under the effect of the pressure of the fluid reigning in the inner duct (C100) of the first element, between a first position retracted into the body (110) of the first element and a second position forward relative to that body. The valve (150) is movable relative to the piston (130) in a direction parallel to the fitting axis of the elements (100, 200) of the connector. The connector comprises sealing means (140) between the piston (130) and the body (110) of the first element (100), at least one member (170) for selectively locking the piston in its first position, and means (270) for maintaining the moving member (170) in the configuration locking the piston (130) in its first position, when the connector (R) is coupled and during separation of the first and second elements (100, 200), at least as long as the valve (150) is not in its position closing off the inner duct (C100) of the first element (100), said maintaining means (270) not acting on the moving locking member (170) in the separated configuration of the connector (R). In the separated configuration of the connector (R), the valve (150) is in the position closing off the inner duct (C100), and the sealing means (140) isolate that duct from the outside, in the two positions of the piston (130) and during the movements thereof between those positions.
