diff --git a/doc/usage/cmd/true.rst b/doc/usage/cmd/true.rst
index f9ef71b..adf6413 100644
--- a/doc/usage/cmd/true.rst
+++ b/doc/usage/cmd/true.rst
@@ -1,3 +1,6 @@
+.. index::
+   single: true (command)
+
 true command
 ============