The invention relates to an assembly between a compressor shaft trunnion and a bevel gear for driving an accessory gearbox of a turbomachine. The assembly comprises a bevel gear, a compressor shaft trunnion arranged coaxially inside the bevel gear, torque transmission means between the compressor shaft trunnion and the bevel gear, a lock nut for preventing the bevel gear from moving axially on the compressor shaft trunnion, the lock nut being suitable for being screwed onto the bevel gear and including a shoulder projecting radially outwards and suitable for coming into axial abutment firstly upstream against a stop nut screwed onto an upstream end of the compressor shaft trunnion, and secondly downstream against a bearing surface of the compressor shaft trunnion, and an anti-rotation pin for preventing the lock nut from rotating.