diff --git a/lisp/progmodes/hideshow.el b/lisp/progmodes/hideshow.el
index 4883150..5e718bf 100644
--- a/lisp/progmodes/hideshow.el
+++ b/lisp/progmodes/hideshow.el
@@ -811,14 +811,14 @@ If `hs-hide-comments-when-hiding-all' is non-nil, also hide the comments."
    (beginning-of-line)
    (run-hooks 'hs-hide-hook)))
 
-(defun hs-show-all ()
+(defun hs-show-all (&optional arg)
   "Show everything then run `hs-show-hook'.  See `run-hooks'."
-  (interactive)
+  (interactive "p")
   (hs-life-goes-on
-   (message "Showing all blocks ...")
+   (when arg (message "Showing all blocks ..."))
    (let ((hs-allow-nesting nil))
      (hs-discard-overlays (point-min) (point-max)))
-   (message "Showing all blocks ... done")
+   (when arg (message "Showing all blocks ... done"))
    (run-hooks 'hs-show-hook)))
 
 (defun hs-hide-block (&optional end)