Dear typing community,

I tried to find if this bug was already reported, but didn't find any mentions.
The following code crashes unexpectedly.

Reproduction steps:

fromtypingimportNamedTupleclassFoo(NamedTuple):defbar(self):print(__class__)

Expected behaviour:

ClassFoo gets created successuflly.

Current behaviour:

RuntimeError: __class__ not set defining 'Foo' as <class '__main__.Foo'>. Was __classcell__ propagated to type.__new__?

Since the bug lives inside of thetyping module I submit this bug report here instead of the python github.

As far as I was able to dig into the code it happens because when_make_nmtuple is called (which eventually callstype.__new__(...)) inside ofNamedTupleMeta.__new__ the__classcell__ object isn't passed along.
Which leads to a runtime error as described inthe documentation

Suggested solution:

• Add"__classcell__" to_special (else__classcell__ will be a attribute of the new NamedTuple).
• Add the following code beforeif Generic in bases:

if"__classcell__"inns:ns["__classcell__"].cell_contents=nm_tpl### already existing code:ifGenericinbases:nm_tpl.__init_subclass__()returnnm_tpl

Version:

Output ofpython -VV:Python 3.13.3 (main, Apr 8 2025, 13:54:08) [Clang 16.0.0 (clang-1600.0.26.6)]

I suspect though that any version >=3.8 is affected.

I haven't yet ever contributed to open source, if appropriate I can open a PR for this fix though.

Best regards,
Robin