Minimum mass of an unseen inner companion that would cause a false positive eccentricity signal in the relative astrometry of GJ 758 A and B by astrometric displacement of GJ 758 A due to their common orbit around the center of mass of the system. The minimum mass is a function of the eccentricity and semi-major axis of the A/B system as well as the maximum epoch difference of all astrometric measurements. Shown are such minimum masses for all orbits with which were recovered for the A/B system. Using our deep SPHERE/IRDIS observations as well as the AMES-COND models Baraffe et al. (2003) we also show the detectable minimum mass at the angular separation at which such a putative inner companion would need to reside. We can exclude the presence of an object that would introduce a false positive eccentricity in all cases.