diff --git a/systemd-mode.el b/systemd-mode.el
index 9c09cac..ba5d162 100644
--- a/systemd-mode.el
+++ b/systemd-mode.el
@@ -35,6 +35,7 @@
 
 (defgroup systemd ()
   "Major mode for editing systemd units."
+  :link '(url-link "http://www.freedesktop.org/wiki/Software/systemd/")
   :group 'tools)
 
 (defcustom systemd-browse-url-function 'eww