  Nuclear shadowing in DIS at moderately small $x$ is suppressed by the nuclear
formfactor and depends on the effective mass of a hadronic fluctuation of the
virtual photon. We propose a solution to the problems (i) of how to combine a
definite transverse size of the fluctuation with a definite effective mass, and
(ii) of how to include the nuclear formfactor in the higher multiple scattering
terms. Comparison of the numerical results with known approximations shows a
substantial difference.
