A nacelle forward part of an aircraft propulsion assembly, includes an air inlet lip at the front end, an internal structure and an external panel extending the lip, and an annular stiffening frame formed around an axis of revolution and comprising an internal peripheral edge linked to the internal structure and an external peripheral edge linked to the external panel. The stiffening frame presents an inclination relative to the axis of revolution, its slope being oriented towards the front end of the nacelle forward part. The stiffening frame is configured to deviate, outside the nacelle of the propulsion assembly, an object striking the stiffening frame. The stiffening frame so configured is capable of withstanding the impacts of objects without breaking while enabling the object striking the stiffening frame to be deviated towards the exterior of the nacelle.