Include "instances of most classes" in a warning about mutable objects
as default values of function/method parameters.
diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex
index c9dd660..1be251e 100644
--- a/Doc/tut/tut.tex
+++ b/Doc/tut/tut.tex
@@ -1388,8 +1388,9 @@
\strong{Important warning:} The default value is evaluated only once.
This makes a difference when the default is a mutable object such as a
-list or dictionary. For example, the following function accumulates
-the arguments passed to it on subsequent calls:
+list, dictionary, or instances of most classes. For example, the
+following function accumulates the arguments passed to it on
+subsequent calls:
\begin{verbatim}
def f(a, L=[]):