Abstract: A lip-operable spill-proof container (1) comprises (A) an open container base (2), (B) a lid element (4) comprising a lid edge (5) mountable on said container base and with a valve seat surface (7) directed to the inside of the container, perpendicular to a longitudinal axis (8) of the container, and (C) an at least partially flexible valve element (11), comprising (1) a valve body (12), (2) a valve flange (13) extending from the valve body with a valve surface (14) that faces said valve seat surface, and (3) a control element (15). The lid element has a carrier (16) positioned inwards from said lid edge (5) and mounted to said lid edge, and the valve element is provided with a mounting rim (17), that engages the carrier (16) and allows movement of the valve element (11) along the longitudinal axis of the container by elastic deformation of the valve element (11).