A way to explain the puzzling difference between the pion form factor as measured in e+ e- annihilations and in tau decays is discussed. We show that isospin symmetry breaking, beside the already identified effects, produces also a full mixing between the rho0, omega and phi mesons which generates an isospin 0 component inside the rho0 meson. This effect, not accounted for in current treatments of the problem, seems able to account for the apparent mismatch between e+ e- and tau data below the phi mass.