diff --git a/doc/lispref/text.texi b/doc/lispref/text.texi
index dc35e93f2da..ec30efe67a3 100644
--- a/doc/lispref/text.texi
+++ b/doc/lispref/text.texi
@@ -5090,6 +5090,7 @@ having an @acronym{HTML} link text that says one thing, while the
 underlying @acronym{URL} points somewhere else.
 
 @cindex suspicious text strings
+@cindex confusable characters
 To help identify these @dfn{suspicious text strings}, Emacs provides a
 library to do a number of checks on text.  (See
 @url{https://www.unicode.org/reports/tr39/, UTS #39: Unicode Security