An unducted fan of variable-pitch blades including roots engaged from outside in respective radial housings of an annular rotor element and guided to turn about their respective axes by pairs of rolling bearings, one of which is carried by an annular segment of a cylindrical skirt mounted in a groove of the annular body and by a locknut screwed onto the cylindrical skit. The bearing is covered externally by a ring including outer dog-clutch teeth co-operating with inner dog-clutch teeth of the housing to hold the ring axially in the housing. A blocking mechanism is engaged between the teeth of the housing and the teeth of the ring preventing the ring from turning and preventing the ring from being withdrawn axially from the housing.