A sub-assembly of a turbine engine including a shaft, a bearing for guiding an axial end of the shaft, a nut which is screw-connected to the end of the shaft and a member for blocking the rotation of the nut in relation to the end of the shaft, wherein the member for blocking the nut includes a first section bearing a plurality of flexible tabs, one end of each tab of which cooperates with a radially inner annular wall of the end of the shaft and includes a second section which cooperates with the nut, characterised in that the second section of the blocking member is screw-connected to the nut and the features of the thread between the blocking member and the nut are different from the features of the thread between the nut and the end of the shaft.