diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index a9b353a22..af5399785 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -237,6 +237,10 @@ Storing links to files using ~org-store-link~ (=<C-c l>=) when
 description of the link, if available.  If no title exists it falls
 back to the filename as before.
 
+*** Change in =org-tags-expand= signature
+
+The function does not allow for a third optional parameter anymore.
+
 * Version 9.4
 ** Incompatible changes
 *** Possibly broken internal file links: please check and fix
diff --git a/lisp/org.el b/lisp/org.el
index 50cace2bb..a8e4d658d 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -11763,7 +11763,7 @@ an accumulator used in recursive calls."
 		(org--tags-expand-group (cdr group) tag-groups expanded))))))
   expanded)
 
-(defun org-tags-expand (match &optional single-as-list downcased)
+(defun org-tags-expand (match &optional single-as-list)
   "Expand group tags in MATCH.
 
 This replaces every group tag in MATCH with a regexp tag search.
@@ -11790,9 +11790,7 @@ will be replaced like this:
 
 When the optional argument SINGLE-AS-LIST is non-nil, MATCH is
 assumed to be a single group tag, and the function will return
-the list of tags in this group.
-
-The DOWNCASED argument is obsolete and has no effect."
+the list of tags in this group."
   (unless (org-string-nw-p match) (error "Invalid match tag: %S" match))
   (let ((tag-groups
          (or org-tag-groups-alist-for-agenda org-tag-groups-alist)))