Upper: KCWI spectrum of the lensed source galaxy smoothed with a 5 pixels kernel, and, lower: of the lens galaxy. The shaded grey region marks sky absorption. The main absorption lines from the source are identified with blue dashed lines on both panels. A template of an ETG (offset vertically to ease legibility) at the same redshift as the source is also shown for comparison. Differences in the global shapes of the continua of the source and template reflect uncertainties in the absolute flux calibration of the KCWI data. The absence of coincidence between the absorption lines from the lens galaxy and from the source supports marginal contamination from the lens and confirms the robustness of the source redshift estimate.