Also, to generalize the concept i would allow @<index> syntax for all arguments (except from constants of course). (Btw, is everyone ok with '@' syntax?) - first change parser's #parseArgument to pass additional argument to requestor, i.e. send #argName: indirectIndex: type: ptrArity: instead of #argName:type:ptrArity: Like that , you won't need to parse it again in NBFFICallout but just check index for being not-nil. Second, refactor NBSTInObjectArgument to be a wrapper around another loader, i.e: NBFnArgument subclass: #NBSTInObjectArgument instanceVariableNames: 'argumentLoader elementIndex' classVariableNames: '' poolDictionaries: '' category: 'NativeBoost-Core-FFI' NBSTInObjectArgument>>emitLoad: gen | baseAddress | argumentLoader emitLoad: gen to: gen asm EAX. gen proxy fetchPointer: elementIndex - 1 ofObject: gen asm EAX. ^ gen asm EAX Like that , a @<index> syntax can be used not just for method arguments but for any other, e.g. self@<index> , ivar@<index> -- Best regards, Igor Stasenko.