  In this paper we determine the tidal distortion parameter k_m of the
secondary partner (mass loser) of the semi-detached eclipsing binary system
V621 Cen by comparing the phenomenologically determined orbital period
P_b=3.683549(11) d to the Keplerian one P^Kep computed with the values of the
relevant system's parameters determined independently of the third Kepler law
itself. Our result is k_m = -1.5 +/- 0.6. Using the periastron precession, as
traditionally done with other eclipsing binaries in eccentric orbits, would
have not been possible because of the circularity of the V621 Cen path.
