Python 3.11.0a6 (main, Mar 7 2022, 16:46:19) [MSC v.1929 64 bit (AMD64)] on win32 Build Boost Python with Visual Studio 2022. Linking my binding to lib file: boost_python311-vc143-mt-x64-1_78.lib Running my binding with: boost_python311-vc143-mt-x64-1_78.dll Upon loading the binding I get; Traceback (most recent call last): File "<stdin>", line 1, in <module> SystemError: type Boost.Python.enum has the Py_TPFLAGS_HAVE_GC flag but has no traverse function The binding runs without problems with Python 3.8-32 and 3.9-64. Any ideas?