diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
index b0700a14190..c084860e903 100644
--- a/Doc/c-api/object.rst
+++ b/Doc/c-api/object.rst
@@ -108,6 +108,9 @@ Object Protocol
    Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
    *opid*.
 
+.. note::
+   If *o1* and *o2* are the same object, :c:func:`PyObject_RichCompareBool`
+   will always return ``1`` for :const:`Py_EQ` and ``0`` for :const:`Py_NE`.
 
 .. cfunction:: PyObject* PyObject_Repr(PyObject *o)