  We analyze the effect of the cosmological expansion on the deflection of
light caused by a point mass, adopting the McVittie metric as the geometrical
description of a pointlike lens embedded in an expanding universe. In the case
of a generic, non-constant Hubble parameter $H$ we derive and approximately
solve the null geodesic equations, finding an expression for the bending angle
$\delta$, which we expand in powers of the mass-to-closest approach distance
ratio and of the impact parameter-to-lens distance ratio. It turns out that the
leading order of the aforementioned expansion is the same as the one calculated
for the Schawarzschild metric and that cosmological corrections contribute to
$\delta$ only at sub-dominant orders. We explicitly calculate these
cosmological corrections for the case of $H$ constant and find that they
provide a correction of order $10^{-11}$ on the lens mass estimate.
