Transmission spectrum of the two sodium doublet lines binned by ×5. Both spectra were generated from HARPS data of HD 189733b. In black is the spectrum from Wyttenbach et al. (2015) with the additional correction of the RM effect. In dark blue is the RM corrected spectrum from Casasayas-Barris et al. (2017) which we use as a reference with permission. The offset between the two high-resolution transmission spectra is consistently below 1σ and the smallest in the line wings, which is the most important range for wind retrieval. Therefore, we consider our RM correction to be sufficient for our purposes.