A low-pressure mercury-vapor discharge lamp, which is equipped with Hg or amalgam, has a pumping tube opening (4) with constricted cross-section or lumen. A solid body in the pumping tube (3) prevents the mercury from emerging into the discharge space. At the same time, the particular shape of the constriction and of the solid body, respectively, makes it possible for Hg vapor to diffuse through-passages between the pumping tube and the solid body into discharge vessel.