Illustration of our method to remove the instrumental polarization in Stokes V spectra for R Leo. Top: Average of Stokes V spectra with low leakage (|M_IV|< 0.01). Center: Example of the correlation between V_instr = M_IV ⋅ I and Stokes I. The regression slope is M_IV = −0.0271. Bottom: Final cleaned and averaged Stokes V spectrum. The vertical plot scale is the same as for the spectrum shown above.