Top panel: stellar spectrum (telluric absorption corrected) of WASP-69 around the Na I doublet. Middle panel: planet transmission spectrum of WASP-69 b in the same wavelength range. The gray data points show the division of in-transit by out-of-transit data, corrected for the changing orbital velocity of the planet. The red filled circles are the data binned by 0.25 Å and the red error bars are the standard deviation of each group of binned data points. Bottom panel: planet transmission spectrum obtained with HARPS-N by Casasayas-Barris et al. (2017), shown for comparison. Both CARMENES and HARPS-N data show a similar pattern.