--- a/src/doc/user/usermanual.sgml
+++ b/src/doc/user/usermanual.sgml
@@ -1075,9 +1075,12 @@
<listitem>
<para>The bottom part allows restricting the search results to a
- sub-tree of the indexed area. If you need to do this often,
- you may think of setting up multiple indexes instead, as the
- performance will be much better.</para>
+ sub-tree of the indexed area. You can use the
+ <guilabel>Invert</guilabel> checkbox to search for files not in
+ the sub-tree instead. If you use directory filtering often and on
+ big subsets of the file system, you may think of setting up
+ multiple indexes instead, as the performance may be
+ better. </para>
</listitem>
</itemizedlist>