We compute by a path integral Monte Carlo calculation the isotropic shift of helium melting pressure in the temperature range (T>100 K) where a discrepancy between theory and experiment has been recently reported. We use a realistic Aziz pair potential together with Bruch-McGee three-body forces for the interaction. The isotopic shift predicted in this work is in agreement with experiment; its measurement provides a good test of the interatomic potential of helium, as the isotopic shift is sensitive to the kinetic energy, which is determined by the short-range pair interaction.