  The mean parallax of the Pleiades open cluster from the Hipparcos catalog is
larger than the true value by approximately 1 mas. The origin of this error, as
well as a possible algorithm of correcting it, was proposed by Makarov (2002).
The problem is reassessed using the more accurate Gaia data with a focus on the
predicted correction to the Pleiades proper motions. The accurately determined
differences Gaia - Hipparcos for 52 common stars are close to these estimates
within the formal uncertainties for all three parameters, which strongly
suggests that the proposed interpretation was correct. With adjustments for the
systematic vector field fitted with 126 vector spherical harmonics to degree 7,
these differences amount to $(+0.39,\,-0.74)$ mas yr$^{-1}$. The implications
of small-scale proper motion and position errors in Hipparcos for present day
astrometry are briefly discussed.
