Mark: Can you please document your change on types.CodeType? In: * https://docs.python.org/dev/library/types.html#types.CodeType * https://docs.python.org/dev/whatsnew/3.11.html The change broke the Genshi project: https://github.com/edgewall/genshi/issues/43 in this Genshi function: def build_code_chunk(code, filename, name, lineno): params = [0, code.co_nlocals, code.co_kwonlyargcount, code.co_stacksize, code.co_flags | 0x0040, code.co_code, code.co_consts, code.co_names, code.co_varnames, filename, name, lineno, code.co_lnotab, (), ()] if hasattr(code, "co_posonlyargcount"): # PEP 570 added "positional only arguments" params.insert(2, code.co_posonlyargcount) return CodeType(*params)