Stack of the spectra (in black) extracted from the MUSE datacube at the multiple image positions of Sys-2. We find evidence for the presence of an emission line at ∼ 6080 Å, which could be interpreted as a CII]1909 doublet (red dotted lines) at z = 2.185, consistent with the redshift estimate obtained with LensTool. The gray vertical bands mark the positions of known sky lines.