diff --git a/README b/README
index de3f066..835941b 100644
--- a/README
+++ b/README
@@ -1,7 +1,8 @@
 systemd mode
 ============
 
-Major mode for editing systemd units in GNU Emacs.
+Major mode for editing systemd units in GNU Emacs.  See the commentary
+in `systemd.el`.
 
 Installation
 ------------