Mining software repositories for bug detection requires accurate techniques of identifying bug-fix revisions. There have been many researches to find exact bug-fix revisions. However there are still noises, we call these noises non-fix hunks, even in exactly identified bug-fix revisions. Our goal is to remove these non-fix hunks automatically. First we inspected every 50 bug-fix revisions of three open source projects (Eclipse, Lucene, and Columba). Among total 2146 hunks we found 179 non-fix hunks. We classified these non-fix hunks into 11 patterns. For all patterns we enumerate enabling static analysis techniques.