Bolometric corrections BC(G) = M_bol − G_abs for the subsample of sources from the Gaia OH/IR stars with good parallaxes. The outlier in the diagram is IRAS 18319-1001, as discussed in the text. The solid curve shows the fit to the data as given in Sect. 5.4, and the broken curve is the bolometric correction as a function of BP–RP colour proposed by Lebzelter et al. (2019) without interstellar extinction.