diff --git a/chapter05/chapter05.xml b/chapter05/chapter05.xml
index 0dce8bf6f..05c68aa36 100644
--- a/chapter05/chapter05.xml
+++ b/chapter05/chapter05.xml
@@ -33,7 +33,7 @@
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gettext.xml"/>
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="grep.xml"/>
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="gzip.xml"/>
-  <!--<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="m4.xml"/>-->
+  <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="m4.xml"/>
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="make.xml"/>
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="patch.xml"/>
   <xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="perl.xml"/>