Hi, I think I found an outdated sentence in the docs and since 'I'm short in time' and the docs says to mail bugs to this mailing list in that case..... https://docs.python.org/3.12/library/functions.html#exec says:

[..] If only globals is provided, it must be a dictionary (and not a subclass of dictionary), which will be used for both the global and the local variables.[..]

but it -- at least seems -- to work fine with a custom dict and if I understand https://github.com/python/cpython/issues/58593 correctly this was changed in Python Version 3.3.