  If the statistics of quasar lensing are to be used to constrain the
cosmological model, the various potential systematic uncertainties in the
deflector population must be accounted for. One ambiguity in the lensing
properties of the dominant deflectors - elliptical galaxies - is their
dynamical normalisation. Assuming they can be modelled as isothermal spheres,
it is shown that their mass normalisation is sufficiently high that current
upper limits on the cosmological constant remain valid, and in fact probably
strengthened, even if ellipticals have significant core radii.
