python · JelleZijlstra · Jul 5, 2025 · Jun 30, 2025 · Jun 30, 2025 · Jun 30, 2025
@@ -1860,7 +1860,9 @@ def _allow_reckless_class_checks(depth=2):
    The abc and functools modules indiscriminately call isinstance() and
    issubclass() on the whole MRO of a user class, which may contain protocols.
    """
-    return _caller(depth) in {'abc', 'functools', None}
+    # gh-136047: When `_abc` module is not available, `_py_abc` is required to
+    # allow `_py_abc.ABCMeta` fallback.
+    return _caller(depth) in {'abc', '_py_abc', 'functools', None}


 _PROTO_ALLOWLIST = {

diff --git a/Misc/NEWS.d/next/Library/2025-07-05-06-59-46.gh-issue-136047.qWvycf.rst b/Misc/NEWS.d/next/Library/2025-07-05-06-59-46.gh-issue-136047.qWvycf.rst
@@ -0,0 +1,2 @@
+Fix issues with :mod:`typing` when the C implementation of :mod:`abc` is not
+available.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix issues with :mod:`typing` when the C implementation of :mod:`abc` is not
		available.