diff --git a/index.xml b/index.xml
index 9afe2b06d..646092548 100644
--- a/index.xml
+++ b/index.xml
@@ -222,6 +222,7 @@
 <!ENTITY c6-m4-inst SYSTEM "chapter6/m4-inst.xml">
 <!ENTITY c6-texinfo SYSTEM "chapter6/texinfo.xml">
 <!ENTITY c6-texinfo-inst SYSTEM "chapter6/texinfo-inst.xml">
+<!ENTITY c6-texinfo-exp SYSTEM "chapter6/texinfo-exp.xml">
 <!ENTITY c6-autoconf SYSTEM "chapter6/autoconf.xml">
 <!ENTITY c6-autoconf-inst SYSTEM "chapter6/autoconf-inst.xml">
 <!ENTITY c6-automake SYSTEM "chapter6/automake.xml">