Fitting the spectral energy distribution of J0956+4046 (top) and J1203+0634 (bottom). The SDSS spectrum (black) and the unreddened SDSS composite (gray) from Vanden Berk et al. (2001). The best extinction modelling is obtained for E(B − V) = 0.27 and a LMC2 extinction law for J0956+4046 (resp. E(B − V) = 0.34 and SMC law for J1203+0634) at the redshift of the absorber. The shaded area represents A_bump, the difference between the best model using Jiang et al. (2011) parametrisation with and without bump. The orange regions at y = 0 indicate the spectral range considered in the fitting process. The right panels show the distributions of E(B − V) (using SMC-law: red, LMC2: green hashed) and A_bump obtained for a control sample of SDSS QSOs (Schneider et al. 2010) within Δz =  ± 0.004 from J0956+4046 (resp. J1203+0634). The arrows indicate the positions of the considered QSO.