Index: Doc/c-api/typeobj.rst
===================================================================
--- Doc/c-api/typeobj.rst	(revision 62359)
+++ Doc/c-api/typeobj.rst	(working copy)
@@ -754,10 +754,11 @@
 .. cmember:: iternextfunc PyTypeObject.tp_iternext
 
    An optional pointer to a function that returns the next item in an iterator, or
-   raises :exc:`StopIteration` when the iterator is exhausted.  Its presence
-   normally signals that the instances of this type are iterators (although classic
-   instances always have this function, even if they don't define a :meth:`next`
-   method).
+   *NULL* when the iterator is exhausted or an error occured while retrieving the next
+   item.  It may set :exc:`StopIteration` exception when the iterator
+   is exhausted. Its presence normally signals that the instances of
+   this type are iterators (although classic instances always have
+   this function, even if they don't define a :meth:`next` method).
 
    Iterator types should also define the :attr:`tp_iter` function, and that
    function should return the iterator instance itself (not a new iterator