  The velocity profile of galaxies around voids is a key ingredient for
redshift space distortion (RSD) measurements made using the void-galaxy
correlation function. In this paper we use simulations to test whether the
velocity profile of the tracers used to find the voids matches the velocity
profile of the dark matter around these voids. A mismatch is expected and found
in the inner part of voids, where tracers are very sparse. We discuss how this
difference is caused by a selection effect where the void centre positions are
correlated to the particular realization of the sparse tracers and their
spatial distribution. In turn, this then affects the RSD void-galaxy
correlation analysis. We show this by evaluating the Jacobian of the real to
redshift space mapping using the tracer or matter velocity profile. Differences
of the order of 20\% in the velocity profile translate into differences of the
order of few percent in the Jacobian. This small discrepancy propagates to the
monopole and quadrupole of the void-tracer correlation function, producing
modifications of comparable magnitude to those from changes in $f\sigma_8$ at
the level of the statistical uncertainties from current analyses.
