To provide a drinking device with a more reliable aerator the invention relates to an infant drinking device (1), comprising a teat (10),a reservoir(60) for holding a liquid, the reservoir (60) being detachably connected to the teat (10) by a connector (50) of the infant drinking device (1), and an aerator (31), such as a duckbill valve, the aerator thereto comprising a deformable opening, for example a slit, such that an internal/external pressure differential during use of the device (1) is reduced in an open position of the opening (35)by allowing air to enter through the opening (35) into the reservoir (60) and such that leakage of fluid from an inside of the drinking device (1) to an outside of the drinking device (1) is hindered in a closed position of the opening (35), wherein the aerator (31) is included in the connector (50) or the teat (10), wherein during assembly of the teat (10), connector (50) and reservoir (60), a minimally defined deformation of the opening (35) of the aerator (31) is enforced by the geometrical and/or material properties of the teat-connector combination.
