A camshaft phaser includes an input member connectable to the crankshaft of an engine; an output member connectable to a camshaft of the engine and defining an advance chamber and a retard chamber with the input member. A valve spool is moveable between an advance position and a retard position and includes a valve spool bore extending thereinto. An insert within the valve spool bore and carries a check valve. The check valve includes a check valve member which moves between a seated position and an unseated position. The check valve also includes a check valve positioning member which is held in compression against an inner periphery of the valve spool bore such that compression of the check valve positioning member holds the check valve in contact with the insert.