diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 198ff7b..ef021dd 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -925,6 +925,10 @@
       >>> list(range(1, 0))
       []
 
+   .. versionchanged:: 3.2
+      Testing integers for membership takes constant time instead of
+      iterating through all items.
+
 
 .. function:: repr(object)