ArgoUML uses both CVS and Bugzilla to keep track of bugfixing activities since 1998. A common practice is to reference source code changes resolving a bug stored in Bugzilla by inserting the id number of the bug in the CVS commit notes. This relationship reveals useful to predict code entities impacted by a new bug report. In this paper we analyze ArgoUML software repositories with a tool, we have implemented, showing what are Bugzilla fields that better predict such impact relationship, that is where knowledge about bug resolution is stored. Categories and Subject Descriptors H.3.1 [Information storage and retrieval]: Content Analysis and Indexing; D.2.7 [Software Engineering]: Distribution, Maintenance, and Enhancement General Terms Measurement, Experimentation Keywords Mining Software Repositories, Impact Analysis