diff --git a/docs/ref/utils.txt b/docs/ref/utils.txt
index c9ab5e3975..19e8361a67 100644
--- a/docs/ref/utils.txt
+++ b/docs/ref/utils.txt
@@ -199,7 +199,8 @@ The functions defined in this module share the following properties:
     Python 2. Under Python 3 it does nothing.
 
     To support Python 2 and 3 with a single code base, define a ``__str__``
-    method returning text and apply this decorator to the class.
+    method returning text (use ``six.text_type()`` if you're doing some
+    casting) and apply this decorator to the class.
 
 .. function:: smart_text(s, encoding='utf-8', strings_only=False, errors='strict')