Seems like a real bug. For an example crash log, see http://build.webkit.org/results/Apple%20MountainLion%20Debug%20WK2%20(Tests)/r169282%20(17813)/js/primitive-property-access-edge-cases-crash-log.txt It looks like it's crashing on all the flavors of debug Mac bots. For test history, see: http://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=js%2Fprimitive-property-access-edge-cases.html No clear revision when the crashes started. Giving it to Geoff first to assign to the appropriate JSC person.