This invention is directed to a flap valve for a dispenser for viscous fluids. More particularly, this invention is directed to a flap valve having a body with a cylindrical valve opening therein, produced by injection molding which is circularly symmetrical to the cylindrical valve opening and extends outwardly around the axis of symmetry, wherein at least one spoke bridges the valve opening diametrically and has a sprue wart in the center thereof, said body cooperating with a flap which closes said cylindrical valve opening, the center part of which flap is arched away from the sprue wart out of the plane of its edge, which edge sealingly fits over the edge of said cylindrical valve opening.