Smalltalk tools register: Browser as: #browser Smalltalk tools openClassBrowser PluggableListMorph was not robust enough Apparently when getListSelector returns a set (like messageList now in 3.0 then getList breaks getList "Answer the list to be displayed. Caches the returned list in the 'list' ivar" getListSelector == nil ifTrue: [^ #()]. list := model perform: getListSelector. list == nil ifTrue: [^ #()]. list := list collectWithIndex: [ :item :index | self wrapItem: item index: index ]. ^ list => fix the problem. I will produce a slice. And I think that the messageList returning a set is a mistake too. getList "Answer the list to be displayed. Caches the returned list in the 'list' ivar" getListSelector == nil ifTrue: [^ #()]. list := (model perform: getListSelector) asArray. list == nil ifTrue: [^ #()]. list := list collectWithIndex: [ :item :index | self wrapItem: item index: index ]. ^ list Stf