Issue #19526: Exclude all new API from the stable ABI.
diff --git a/Include/sysmodule.h b/Include/sysmodule.h
index 925c2a3..79e52a3 100644
--- a/Include/sysmodule.h
+++ b/Include/sysmodule.h
@@ -8,7 +8,9 @@
 #endif
 
 PyAPI_FUNC(PyObject *) PySys_GetObject(const char *);
+#ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject *) _PySys_GetObjectId(_Py_Identifier *key);
+#endif
 PyAPI_FUNC(int) PySys_SetObject(const char *, PyObject *);
 PyAPI_FUNC(int) _PySys_SetObjectId(_Py_Identifier *key, PyObject *);