diff --git a/lisp/org.el b/lisp/org.el
index 5ae8ddc70..879821e60 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -5720,7 +5720,8 @@ If yes, remember the marker and the distance to BEG."
 
 (defun org-sort (with-case)
   "Call `org-sort-entries-or-items' or `org-table-sort-lines'.
-Optional argument WITH-CASE means sort case-sensitively."
+Optional argument WITH-CASE means sort case-sensitively.
+With a double prefix argument, also remove duplicate entries."
   (interactive "P")
   (if (org-at-table-p)
       (org-call-with-arg 'org-table-sort-lines with-case)