Hi, I am experiencing problems in using #flatCollect: on a SortedCollection. This reproduces my problem: ((OrderedCollection with: #(1 2 3) with: #(3 4 5)) asSortedCollection: [ :a :b | true ]) flatCollect: #yourself I am using the last Pharo 2.0 image from the CI server (ZeroConf script). SortedCollection(Object)>>shouldNotImplement SortedCollection>>at:put: WriteStream>>pastEndPut: WriteStream>>nextPut: WriteStream(Stream)>>nextPutAll: in Block: [:v | self nextPut: v] Array(SequenceableCollection)>>do: WriteStream(Stream)>>nextPutAll: WriteStream>>nextPutAll: SortedCollection(Collection)>>flatCollect: in Block: [:each | stream... SortedCollection(OrderedCollection)>>do: SortedCollection(Collection)>>flatCollect: Thanks for any help, Roby