While Fuel was trying to serialize a sort block ([ :a :b | a name < b name ]), I got CompiledMethod>>errorSubscriptBounds:. One strange thing about the block is that the outerContext is `SortedCollection>>DoIt`, meaning I probably had to initialize it by hand due to a previous Fuel problem. The odd thing about the error is that this object graph was serializing and materializing just fine before I upgraded Pharo Launcher. Call chain: CompiledMethod(Object)>>errorSubscriptBounds: CompiledMethod(Object)>>at: InstructionStream>>interpretNextV3PlusClosureInstructionFor: OpalEncoderForV3PlusClosures class>>interpretNextInstructionFor:in: InstructionStream>>interpretNextInstructionFor: [ (InstructionStream new method: self pc: pc) interpretNextInstructionFor: nil ] in CompiledMethod(CompiledCode)>>abstractBytecodeMessageAt: in Block: [ (InstructionStream new method: self pc: pc)... BlockClosure>>on:do: CompiledMethod(CompiledCode)>>abstractBytecodeMessageAt: BlockClosure>>blockCreationBytecodeMessage BlockClosure>>endPC BlockClosure>>abstractBytecodeMessagesDo: BlockClosure>>isClean BlockClosure>>shouldBeSubstitutedByCleanCopy BlockClosure>>fuelAccept: FLLightGeneralMapper>>mapAndTrace: ----- Cheers, Sean -- Sent from: http://forum.world.st/Pharo-Smalltalk-Developers-f1294837.html