We discuss the antiGZK effect in the diffusive propagation of ultra high energy protons in intergalactic magnetic fields , which consists in a jump-like increase of the maximum distance from which ultra high energy protons can reach an observer . The position of this jump , E _ { j } \approx 2 \times 10 ^ { 18 } eV , is determined exclusively by energy losses ( transition from adiabatic to pair-production energy losses ) and it is independent of the diffusion parameters . The diffuse spectrum presents a low-energy steepening approximately at this energy , which is very close to the position of the second knee observed in the cosmic ray spectrum . The dip , seen in the universal spectrum as a signature of the interaction with the cosmic microwave background radiation , is also present in the case of diffusive propagation in magnetic fields .