A valve for the venting circuit of a liquid tank including a main chamber which opens into the tank and is connected via an aperture to the venting circuit, a float comprising a body, and a head capable of closing off the orifice. The float being able to slide vertically inside the main chamber. The valve further including a baffle surrounding the aperture and defining a secondary chamber via the bottom inside the main chamber. The dimensions and the shape of the secondary chamber, of the body of the float, and of the head of the float are designed so that the head can slide at least partly inside the secondary chamber, while the body of the float cannot do so.