A method for determining corrections to features of a mask. The method includes obtaining (i) a pattern group for a design layout, and (ii) defect inspection data of a substrate imaged using the mask used in the patterning process for the design layout; determining, based on the defect inspection data, a defect map associated with the pattern group, wherein the defect map comprises locations of assist features having a relatively higher probability of being printed on the substrate compared to other patterns of the design layout; and determining, via simulating an optical proximity correction process using data associated with the defect map, corrections to the features of the mask.