When loading a package with class definitions containing a trait composition like ClassX uses: TraitY - {#selector}, the composition is lost in the image. It seems closely related to previous issues 2477 and 2148 But I am not sure if this is the same bug reappearing or a variant. To reproduce: Gofer new squeaksource: 'MooseAlgos'; package: 'Moose-Algos-Graph'; package: 'Moose-Tests-Algos-Graph'; load Run tests in Moose-Tests-Algos-Graph: you should have 3 failures and 4 errors, all due to the missing trait composition in some classes. After loading, you can make a diff changes in monticello, it will highlight the package as dirty and show you the lost trait compositions in two classes: MOGraphNode subclass: #MABfsNode uses: MATEdgeNode - {#previousEdges. #from:edge:} instanceVariableNames: 'nextEdges firstDepth' classVariableNames: '' poolDictionaries: '' category: 'Moose-Algos-Graph' MODisjointSetNode subclass: #MANextNode uses: MATNodeNode - {#from:. #previousNodes} instanceVariableNames: 'nextNodes' classVariableNames: '' poolDictionaries: '' category: 'Moose-Algos-Graph' The problem has been reproduced in 11383 and 11400 RC2. -- Simon