The X-ray (top) and optical/NIR (bottom) light curves of GRB 121217A with the inset graph showing the GBM prompt emission of the second peak. The canonical model of the X-ray emission can be seen as the black-dashed line in the top panel, where the flare, simultaneous to the second prompt peak, has been excluded from the fit (Sect. 3.3). The black-dashed line in the lower panel is the best-fit double broken power law of the afterglow emission (Sect. 3.4). Only the observations with a time less than T₀ + 10⁴   s have been included and the full light curve can be seen in Fig. A.1.