(describe-categories): Doc fix.

1 files changed, 3 insertions, 1 deletions

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index 9769d613cbc..4201a3de1a5 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -544,7 +544,9 @@ BUFFER defaults to the current buffer."
 ;;;###autoload
 (defun describe-categories (&optional buffer)
   "Describe the category specifications in the current category table.
-The descriptions are inserted in a buffer, which is then displayed."
+The descriptions are inserted in a buffer, which is then displayed.
+If BUFFER is non-nil, then describe BUFFER's category table instead.
+BUFFER should be a buffer or a buffer name."
   (interactive)
   (setq buffer (or buffer (current-buffer)))
   (help-setup-xref (list #'describe-categories buffer) (interactive-p))