diff --git a/Doc/ref/ref4.tex b/Doc/ref/ref4.tex
index 6e893f1..00f3058 100644
--- a/Doc/ref/ref4.tex
+++ b/Doc/ref/ref4.tex
@@ -197,5 +197,12 @@
 exception handler as additional information.  For class exceptions,
 this object must be an instance of the exception class being raised.
 
+\begin{notice}[warning]
+Messages to exceptions are not part of the Python API.  Their contents may
+change from one version of Python to the next without warning and should not
+be relied on by code which will run under multiple versions of the
+interpreter.
+\end{notice}
+
 See also the description of the \keyword{try} statement in section
 \ref{try} and \keyword{raise} statement in section \ref{raise}.