diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index 02064e7a374..5869f53636c 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -2985,10 +2985,6 @@ highlighted (instead of the entire text that @var{matcher} matched).
 ("fu\\(bar\\)" . 1)
 @end example
 
-If you use @code{regexp-opt} to produce the regular expression
-@var{matcher}, you can use @code{regexp-opt-depth} (@pxref{Regexp
-Functions}) to calculate the value for @var{subexp}.
-
 @item (@var{matcher} . @var{facespec})
 In this kind of element, @var{facespec} is an expression whose value
 specifies the face to use for highlighting.  In the simplest case,