Hi there, Iâve just hit an issue that prevented to open packages in monticello MessageNotUnderstood: receiver of "indexOf:" is nil UndefinedObject(Object)>>doesNotUnderstand: #indexOf: MCFileRepositoryInspector>>packageSelection PluggableListMorph>>getCurrentSelectionIndex PluggableListMorph>>updateList PluggableListMorph>>update: MCFileRepositoryInspector(Object)>>changed: in Block: [ :aDependent | aDependent update: aParameter ] DependentsArray>>do: MCFileRepositoryInspector(Object)>>changed: MCFileRepositoryInspector>>refresh MCFileRepositoryInspector>>setRepository:workingCopy: in Block: [ ... BlockClosure>>newProcess in Block: [ ... This is what Iâm using as hacky workaround: MCFileRepositoryInspector>>packageSelection ^ self packageList isNil ifTrue:[ 1 ] ifFalse:[ self packageList indexOf: selectedPackage ] The problem is that packageList is nil for some reason. Looks like filetree is involved since 1. Iâm using it and 2. it sets an extension method #refresh that makes packageList := nil sebastian o/ blog: http://sebastianconcept.com LinkedIn: http://www.linkedin.com/in/sebastiansastre github: https://github.com/sebastianconcept