#8578: mention danger of not incref'ing weak referenced object.
diff --git a/Doc/c-api/weakref.rst b/Doc/c-api/weakref.rst
index 081419d..8a36110 100644
--- a/Doc/c-api/weakref.rst
+++ b/Doc/c-api/weakref.rst
@@ -53,7 +53,14 @@
.. cfunction:: PyObject* PyWeakref_GetObject(PyObject *ref)
Return the referenced object from a weak reference, *ref*. If the referent is
- no longer live, returns ``None``.
+ no longer live, returns :const:`Py_None`.
+
+ .. warning::
+
+ This function returns a **borrowed reference** to the referenced object.
+ This means that you should always call :cfunc:`Py_INCREF` on the object
+ except if you know that it cannot be destroyed while you are still
+ using it.
.. cfunction:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)