The invention discloses a high-pressure piston compressor (1) for compressing gas, comprising a vessel (4) having a vessel chamber (8, 23) wherein a piston (3) is guided reciprocally, for compressing a gas in the vessel chamber during operation of the piston compressor, an inlet valve housing (17, 29) comprising an inlet valve(18, 30), and an outlet valve housing (15, 31) comprising an outlet valve (16, 32), wherein the inlet valve housing and the outlet valve housing are mounted within a portion of the vessel chamber wall (14, 28), and wherein the portion of the vessel chamber wall encloses the inlet valve housing and the outlet valve housing, such that the portion of the vessel chamber wall generates an isostatic counter-pressure on the inlet valve housing and the outlet valve housing in response to the pressure on the inlet valve housing and the outlet valve housing from the gas in the vessel chamber during operation of the piston compressor.