A sliding block for a piston of a hydraulic piston machine, includes a concave recess to receive a piston head and a sliding surface to support the piston. A lubricant channel passes through the sliding block from the concave recess to the sliding surface, and the concave recess transforms with a constant tangent i.e. without kinking into a transition segment of a constantly narrowing taper segment of the lubricant channel. The transition segment is convex.