Spectral energy distribution of the afterglow of GRB 060526 in uvw2uvm2uvw1uBg′Vr′R_Ci′I_CJHK_S, and fits with no extinction (straight black line), MW extinction (dotted line), LMC extinction (dashed line) and SMC extinction (thick dash-dotted line). The fit with MW dust finds (unphysical) negative extinction, causing an “emissive component” instead of a 2175 Å absorption bump. Data beyond 2.2 × 10¹⁵ Hz (Vg′Buuvw1uvm2uvw2) were not included in the fit due to Lyman forest blanketing, the grey curves represent extrapolations. The extinction curves of Pei (1992) are not correctly defined beyond 3.2 × 10¹⁵ Hz. The UVOT UV filters are upper limits only, showing the strong flux decrease beyond the Lyman cutoff. The flux density scale is measured at the break time.