(diary-mail-addr): Fix custom type.

diff --git a/lisp/calendar/diary-lib.el b/lisp/calendar/diary-lib.el
index 2a27d506eb5c389c0a65755afabbcfcb33edc0ce..8a46d4dcb66a682b9b3092f8fe247c003f4faedb 100644 (file)
--- a/lisp/calendar/diary-lib.el
+++ b/lisp/calendar/diary-lib.el
@@ -589,7 +589,7 @@ is created."
   (if (boundp 'user-mail-address) user-mail-address nil)
   "*Email address that `diary-mail-entries' will send email to."
   :group 'diary
-  :type 'string
+  :type '(choice string (const nil))
   :version "20.3")
 
 (defcustom diary-mail-days 7