diff --git a/lisp/vc/vc-rcs.el b/lisp/vc/vc-rcs.el
index 9dffc144c6..0a10449763 100644
--- a/lisp/vc/vc-rcs.el
+++ b/lisp/vc/vc-rcs.el
@@ -177,6 +177,8 @@ vc-rcs-dir-status-files
 	  (push (list frel state) result))))
     (funcall update-function result)))
 
+(defun vc-rcs-dir-extra-headers (&rest ignore))
+
 (defun vc-rcs-working-revision (file)
   "RCS-specific version of `vc-working-revision'."
   (or (and vc-consult-headers