Defect repair is a key component in fabricating a defect- free mask. Focused ion beam repair has been successfully used for x-ray masks. To repair an opaque defect the ion beam is used to mill away the excess absorber while clear defect repair requires beam assisted deposition of Au. Current x-ray mask repair tools specify edge placement accuracy of +/- 25 mask nm. However, the effects of non- ideal repairs on printed resist have not been investigated, and the tolerance of such errors have not been specified. In this study, reported defect printing was tracked and resists edge placement accuracy was measured to evaluate the non- ideal repair effects. In the opaque defect repair case, we observed inside the 'repair box', repaired mask errors such as sloped walls, remaining absorber and re-deposition outside the box and found that these errors shift the printed resist pattern edge toward the inside of the box. In the clear defect repair case, the deposited gold is typically extended out of the defined box by sloped side- wall and the printed resist pattern edge is shifted toward the outside of the box. These non-ideal repairs systematically affect resist pattern edge placement. An x- ray lithography simulation tool was used to analyze these effects. Preliminary by adjusting the 'repair box' size and etch/deposition time, the effects of non-ideal repair can be eliminated. Programmed defects were created on a mask and repairs were performed, evaluated and optimized with actual x-ray exposures.