A control valve for a hydraulic device, in particular a central valve of a camshaft adjuster for a reciprocating-piston internal combustion engine, having a holding component (1) in which a valve housing (3), a control sleeve (2) and a control piston (4) are arranged, wherein the control piston (4) is mounted so as to be loaded on one side by a spring and, on the other side, is mounted with limited axial displaceability in the control sleeve (2) by means of a locking ring (6), wherein the locking ring (6) can be fastened in the axial direction in an inner holder (14) on the holding component (1) and can be connected by a fixing device to a component of the control valve, and wherein the fixing device has fastening elements attached to the locking ring (6) and has matching recesses (10) in the valve housing (3) and/or in the control sleeve (2).