A camshaft phaser includes an input member; an output member defining an advance chamber and a retard chamber with the input member; a camshaft phaser attachment bolt which clamps the camshaft phaser to a camshaft, the camshaft phaser attachment bolt having a bolt valve bore extending along an axis. A valve sleeve is located coaxially within the bolt valve bore such that an annular clearance is provided radially therebetween. A valve spool is located coaxially within the valve sleeve such that the valve spool is moved coaxially between an advance position and a retard position. A compliant sealing ring radially between the bolt valve bore and the valve sleeve prevents fluid communication through the annular clearance axially between opposing axial sides of the sealing ring and isolates the valve sleeve from radial expansion of the camshaft phaser attachment bolt.