A closing plug for closing holes in objects, in particular for closing holes in vehicle bodies, wherein the closing plug has at least one first circumferential wall which encloses a cavity, wherein a transverse wall is present in the cavity between the circumferential side wall, which transverse wall has an outer shape which corresponds to the shape of the cavity and is attached to the side wall in a circumferential manner, wherein, for the purpose of reinforcing the circumferential wall against yielding outward or inward, at least one reinforcement rib extends transversely through the cavity and so as to connect opposite regions of the circumferential side wall.