This test illustrate the problem: testMethodPackageFromObsoleteClass | pack method | pack := self createNewPackageNamed: 'P1'. foo := self createNewClassNamed: #FooForTest inPackage: pack. foo compileSilently: 'bar ^42'. method := foo>>#bar. foo removeFromSystem. self assert: (method packageFromOrganizer: pack organizer)equals: foo package. This seems to happen in non silent tests that - create a class/trait for test - sends an announcement with a compiled method instance (like, method recategorized) - remove the class/trait because they are for test only :) - then, since the announcements are handled asychronously, a method from an obsolete category reaches somewhere, and RPackage explodes. WIll open an issue. Guille