diff --git a/lisp/obsolete/rnewspost.el b/lisp/obsolete/rnewspost.el
index 3dbeb5d871a..221f1a0e675 100644
--- a/lisp/obsolete/rnewspost.el
+++ b/lisp/obsolete/rnewspost.el
@@ -60,6 +60,8 @@
 (require 'sendmail)
 (require 'rnews)
 
+(defvar mail-reply-buffer)
+
 (defvar news-reply-mode-map () "Mode map used by news-reply.")
 
 (or news-reply-mode-map