  The deuteron charge radius is calculated from the measurement of the Lamb
shift in muonic deuterium, taking into account the electron vacuum polarization
correction to the nuclear-structure effects. This correction is unexpectedly
large and gives a mean-square charge-radii difference $ r_d^2-r_p^2 =
3.81747(346)\, {\rm fm}^2 $, which is now consistent with that obtained from
the ordinary H-D isotope shift in the 1$S$-2$S$ transition. This suggests that
the long-standing discrepancy in the proton charge radius obtained from
electronic and muonic systems is due to an underestimated uncertainty in
ordinary hydrogen spectroscopy.
