A packaging assembly includes a bottle, which may be used upside-down such that a neck is turned towards the ground, and a closure without any added seal gasket for closing the neck. This closure includes a cap for obturating the neck, and a skirt for attachment to the neck. The cap includes an inner sealing lip, delimiting on its outer face, a convex tight bearing surface for bearing tightly against the inner face of the neck, and a substantially flat ramp surface, which connects the tight bearing surface to a lower axial end of the lip, and which, while the lip is deformed with the remainder of the closure when an inner clip of the skirt interferes with an outer bead of the neck during placement of the closure on the neck, may interfere with a free end of the neck to guide engagement of the lip inside the neck.