diff --git a/reference/session/sessionhandler.xml b/reference/session/sessionhandler.xml
index c47d7b310b..613809c036 100644
--- a/reference/session/sessionhandler.xml
+++ b/reference/session/sessionhandler.xml
@@ -133,6 +133,14 @@ session_start();
 ]]>
     </programlisting>
    </example>
+   <note>
+    <para>
+     Since this class' methods are designed to be called internally by PHP as part of the normal session workflow,
+     child class calls to parent methods (i.e. the actual internal native handlers) will return &false; unless
+     the session has actually been started (either automatically, or by explicit <function>session_start</function>.
+     This is important to consider when writing unit tests where the class methods might be invoked manually.
+    </para>
+   </note>
   </section>
 
  </partintro>