A device for mixing two pasty substances is provided with a housing including an essentially tubular section having two radial inlet openings at a rear end and an outlet opening at a front end of the tubular section, and a driveable mixer shaft extending through the tubular section and rotatably supported in the housing. The mixer shaft includes multiple rigid mixer elements protruding from an axis for mixing the two pasty substances when they pass through the tubular section. The mixer shaft includes at the level of the inlet openings at least one deflection element for promoting the axial transportation of the two pasty substances when fed through the inlet openings, wherein the at least one deflection element has a deflection surface extending about the axis and at an inclination to a radial plane of the axis.