Hi Debugging a Fuel test case, I discovered something I can't explain myself: Project class>>#spawnNewProcess is replaced in the middle of the *first* test run, between serialization and materialization. This happens the *first time* I run the test in a *clean* Pharo 1.3 image, after first time, the method doesn't change anymore. In 1.4 we don't have to problem. I logged the method sources, and actually there is a difference: -- during serialization -- 'spawnNewProcess UIProcess := [[World doOneCycle. Processor yield. false] *whileFalse.* * nil*] newProcess priority: Processor userSchedulingPriority. UIProcess resume' -- during materialization -- 'spawnNewProcess UIProcess := [ [World doOneCycle. Processor yield. false] *whileFalse: [].* * *] newProcess priority: Processor userSchedulingPriority. UIProcess resume' -- system info -- Pharo1.3 - 13327 - 'Croquet Closure Cog VM [CoInterpreter VMMaker-oscog-EstebanLorenzano.139]' Do you know why this happens? Thanks, MartÃn