diff --git a/doc/emacs/custom.texi b/doc/emacs/custom.texi
index 094b8b11f6a..2d63b2a7175 100644
--- a/doc/emacs/custom.texi
+++ b/doc/emacs/custom.texi
@@ -2434,6 +2434,9 @@ keys which send non-@acronym{ASCII} characters.
 Write a single-quote (@code{'}) followed by the Lisp object you want.
 @end table
 
+  For more information on the Emacs Lisp syntax, @pxref{Introduction,,,
+elisp, The Emacs Lisp Reference Manual}.
+
 @node Init Examples
 @subsection Init File Examples