Variable gwIMF in the stellar mass regime (0.4–0.8 M_⊙) for 6 UFDs shown by the coloured points from Gennaro et al. (2018b). The IGIMF1 models (given by two slopes α₁ = 1.3 and α₂ = 2.3) are represented by the horizontal green line. These have the same effective invariant slope as the canonical IMF in this mass regime. The IGIMF3 metallicity-dependent effective slope based on Eq. (10) is shown in red. These data may indicate the necessity for a different dependency of the α_1,2 indices on metallicity than represented by Eq. (10). This different dependency is indicated by the orange dot-dashed line (Eq. (18)).