The distance of the members of NGC 6231 (blue histogram) and the most probable distance of HD 153919 (1.58 kpc, black line) with the corresponding distance interval (red and green lines). The average Gaia EDR3 distance to the cluster is 1.63 kpc, similar to the value determined by Sana et al. (2006) (1.64 kpc) and Sung et al. (2013) (1.59 kpc), both determined with the so-called spectroscopic parallax method (based on the spectral type of the star and the reddening).