Observer-frame optical (griz) LCs of GRB 161219B/SN 2016jca. Left: LCs of the AG, SN and underlying host, which are uncorrected for extinction. The typical evolution from the AG-dominated to the SN-dominated phase is seen in all optical filters. Right: host- and AG-subtracted LCs of SN 2016jca. A pre-maximum bump is seen in the g-band, which peaks around ≈5–6 days. This bump is conspicuously absent in the other filters, and the origin of this flux excess is discussed in Sect. 9. In contrast, the potential bump seen in the z-band LC around 10 days is not real, but arises from instrumental defects.