diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 643464b..2dd85f4 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -356,7 +356,8 @@
 
 .. cmdoption:: -3
 
-   Warn about Python 3.x incompatibilities. Among these are:
+   Warn about Python 3.x incompatibilities which cannot be fixed trivially by
+   :ref:`2to3 <2to3-reference>`. Among these are:
 
    * :meth:`dict.has_key`
    * :func:`apply`