diff --git a/lisp/files.el b/lisp/files.el
index f76b08f4cb7..3c5905d2164 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -6705,7 +6705,7 @@ If DIR's free space cannot be obtained, this function returns nil."
   (save-match-data
     (let ((avail (nth 2 (file-system-info dir))))
       (if avail
-	  (format "%.0f" (/ avail 1024))))))
+          (file-size-human-readable avail)))))
 
 ;; The following expression replaces `dired-move-to-filename-regexp'.
 (defvar directory-listing-before-filename-regexp