  The electromagnetic contribution to the isomultiplet mass splittings of heavy
mesons is reanalyzed within the framework of the heavy mass expansion.
  It is shown that the leading term in the expansion is given to a good
approximation by the elastic term. $1/m_{Q}$-corrections can only be estimated,
the main source of uncertainty now being inelastic contributions. The
$1/m_{Q}$-corrections to the elastic term turn out to be relatively small in
both D and B pseudoscalar mesons.
