A locking mechanism for first and second housing parts of a housing of a plug connector, includes a push button, which extends in the axial longitudinal direction through an opening of the first housing part into the interior of the housing. The push button is movably arranged, relative to the housing, between predetermined first and second axial positions, which correspond with the first and second positions of the housing parts. The push button and an interior locking element are configured such that the push button is in pressure contact to the locking element and interacts with the locking element such that, in the case of movement of the push button from the first to the second positions a radial pressure contact between the two housing parts is provided such that a gap between the first and second housing parts is minimized.