diff --git a/lisp/indent-aux.el b/lisp/indent-aux.el
index 27d5875bc22..eeb8f1ee6bb 100644
--- a/lisp/indent-aux.el
+++ b/lisp/indent-aux.el
@@ -45,10 +45,14 @@ is yanked."
           end (max a b)))
   (let ((indentation (save-excursion (goto-char beg)
                                      (current-column)))
+        (i-t-m indent-tabs-mode)
         (text (if delete
                   (delete-and-extract-region beg end)
                 (buffer-substring beg end))))
     (with-temp-buffer
+      ;; Indent/deindent the same as the major mode in the original
+      ;; buffer.
+      (setq indent-tabs-mode i-t-m)
       (insert text)
       (indent-rigidly (point-min) (point-max)
                       (- indentation))