diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 9a9c707dc177a9..dff719e83ddf99 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -862,7 +862,8 @@ are always available.  They are listed here in alphabetical order.
    Return ``True`` if *class* is a subclass (direct, indirect or :term:`virtual
    <abstract base class>`) of *classinfo*.  A
    class is considered a subclass of itself. *classinfo* may be a tuple of class
-   objects, in which case return ``True`` if *class* is a subclass of any entry
+   objects (or recursively, other such tuples),
+   in which case return ``True`` if *class* is a subclass of any entry
    in *classinfo*.  In any other case, a :exc:`TypeError` exception is raised.