diff --git a/doc/emacs/frames.texi b/doc/emacs/frames.texi
index 3ee6eb59dbb..ce631561be7 100644
--- a/doc/emacs/frames.texi
+++ b/doc/emacs/frames.texi
@@ -334,6 +334,7 @@ In this way, you can use the mouse to move point over a button without
 activating it.  Dragging the mouse over or onto a button has its usual
 behavior of setting the region, and does not activate the button.
 
+@vindex mouse-1-click-follows-link
   You can change how @kbd{mouse-1} applies to buttons by customizing
 the variable @code{mouse-1-click-follows-link}.  If the value is a
 positive integer, that determines how long you need to hold the mouse