GROND g′r′i′z′-band light curves of the afterglow of GRB 090510 (from bottom to top). For reasons of clarity the g′,i′,z′ bands were shifted by  + 1.4, − 1.0, − 2.0 mag, respectively. The solid straight line is the best fit of the r′-band data, and the broken lines are its corresponding shifts to the other bands. Shown are all data points with a 1σ error of  ≲ 0.35 mag (see Table A.1).