diff --git a/doc/usage/cmd/source.rst b/doc/usage/cmd/source.rst
index 697f644..0de5f33 100644
--- a/doc/usage/cmd/source.rst
+++ b/doc/usage/cmd/source.rst
@@ -1,6 +1,9 @@
 .. SPDX-License-Identifier: GPL-2.0+
 .. Copyright 2022, Heinrich Schuchardt <xypron.glpk@gmx.de>
 
+.. index::
+   single: source (command)
+
 source command
 ==============