Hi Tommaso and I, while hacking on Fuel, today discovered that globals in Pharo can have very weird bindings (I guess some of you already know that). For example: class := Class new setName: 4; yourself. Smalltalk at: class name put: class. So we now have a class with name 4 (which is a SmallInteger): self assert: (Smalltalk at: 4) == class. There are basically two different issues: 1. SystemDictionary will store any kind of association, not only symbols / strings 2. SystemDictionary is an IdentityDictionary and as such two equivalent but not identical keys will not resolve to the same object: class := Class new setName: (String streamContents: [ :s | s nextPutAll: 'someName']); yourself. Smalltalk at: class name put: class. Smalltalk at: (String streamContents: [ :s | s nextPutAll: 'someNameâ]) ifAbsent: [ false ]. âââ> falseâ In Fuel we simply assume that any key to a global is either a ByteString or ByteSymbol. If thatâs not the case bad things happen. It would help us a lot if we could clear up the semantics of bindings in SystemDictionary: 1. Are bindings with keys that are not ByteString or ByteSymbol valid? 2. Should we keep allowing ByteString as keys to globals (ByteSymbol guarantees identity)? 3. If we allow ByteString, do we also allow WideString? 4. Would âtype checksâ on SystemDictionary incur a big performance penalty? Any suggestions are welcome. Cheers, Max