diff --git a/Documentation/BaseAdditions.gsdoc b/Documentation/BaseAdditions.gsdoc
index 39fc0dca1..28c06ab95 100644
--- a/Documentation/BaseAdditions.gsdoc
+++ b/Documentation/BaseAdditions.gsdoc
@@ -25,6 +25,7 @@
     </chapter>
     <back>
       <index scope="project" type="class" />
+      <index scope="project" type="category" />
       <index scope="project" type="protocol" />
     </back>
   </body>