Repair experiments to remove opaque defects on silicon X-ray masks with electroplated gold absorber features were performed using a 100 keV focussed ion beam system. The quality of the milling process was checked by transferring the repaired mask patterns with X-rays into a resist. The influence of the parameters affecting the repair accuracy such as ion image quality, defect localisation, redeposition, milling strategy, and microcrystallites in the electroplated gold absorber on X-ray masks are discussed.