diff --git a/lisp/gnus/gnus-group.el b/lisp/gnus/gnus-group.el
index 365b0ab4ba4..f3dcc40b8c4 100644
--- a/lisp/gnus/gnus-group.el
+++ b/lisp/gnus/gnus-group.el
@@ -2459,7 +2459,7 @@ the bug number, and browsing the URL must return mbox output."
     (let ((coding-system-for-write 'binary)
 	  (coding-system-for-read 'binary))
       (with-temp-file tmpfile
-	(mm-enable-multibyte)
+	(mm-disable-multibyte)
 	(dolist (id ids)
 	  (url-insert-file-contents (format mbox-url id)))
 	(goto-char (point-min))