  We examine the effect of the difference in nuclear interactions of ${K}^0$
and $\bar{K}^0$ mesons on the measurement of CP asymmetry for experiments at
$e^+e^-$ colliders - charm and $B$-meson factories. We find that this effect on
CP asymmetry can be as large as 0.3%, and therefore sufficiently significant in
interpreting measurements of CP asymmetry when neutral kaons are present in the
final state.
