Combined GROND and XRT spectral energy distribution extracted around 11 ks as discussed in Sect. 4. The dashed line represents the unabsorbed single power-law connecting the X-rays with the NIR bands and characterised by a spectral index β = 1.00 ± 0.01. The solid line represents the same absorbed model with mag and . Note that the g′ (and partially the r′) bands are strongly affected by the Lyman break at z = 3.8.