Normalised X-shooter spectra from t_max+32.7 days to t_max+94.3 days (top panels) and their inverse-variance weighted co-added spectrum (bottom panel). The individual and stacked spectra show barely resolved, narrow absorption lines from the host ISM (marked by the solid vertical lines). In addition, a blue-shifted (2918 km s⁻¹) absorption line system is visible (marked by the dashed vertical lines). The FWHMs of the blue-shifted component are 406 km s⁻¹, significantly larger than the ISM lines but significantly smaller than the SN lines. This blue-shifted absorption-line system is connected with a shell of circumstellar material expelled by the progenitor star shortly before the explosion. No significant evolution in the position or shape of the absorption lines can be seen in the individual spectra (upper panels). The error spectrum is shown in grey.