diff --git a/Doc/Sd1/appendix.xml b/Doc/Sd1/appendix.xml
index 0449252e91f8755cab74bbfec35a985621d12e3f..c73bf4feefde63adcb7188c71a43b1d47cdba3f6 100644
--- a/Doc/Sd1/appendix.xml
+++ b/Doc/Sd1/appendix.xml
@@ -479,7 +479,7 @@ java -jar ~/.m2/repository/de/hdm-stuttgart/mi/sd1/grep/0.9/grep-0.9.jar $*
 The red cross acts worldwide</programlisting>
           </listitem>
 
-          <listitem>
+          <listitem xml:id="sd1ProjectGrepUnitTestingHint">
             <para>Testing requires capturing of output being generated by e.g.
             <methodname
             xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/System.html#out">System.out</methodname><code>.</code><methodname