diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index ce83757..a513d40 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -2208,6 +2208,10 @@
       See :class:`collections.Counter` for a complete implementation including
       other methods helpful for accumulating and managing tallies.
 
+      .. versionchanged:: 3.3
+         If the dict is modified during the lookup, a :exc:`RuntimeError`
+         exception is now raised.
+
    .. describe:: d[key] = value
 
       Set ``d[key]`` to *value*.