(cal-tex-preamble-extra): Fix custom type.

diff --git a/lisp/calendar/cal-tex.el b/lisp/calendar/cal-tex.el
index c75231e4ace856a369269a2c713275a7572cf47f..b1380c2a9131ac67cc8b4ab97870f3bf49e8162d 100644 (file)
--- a/lisp/calendar/cal-tex.el
+++ b/lisp/calendar/cal-tex.el
@@ -144,7 +144,7 @@ At present, this only affects `cal-tex-cursor-day'"
   "A string giving extra LaTeX commands to insert in the calendar preamble.
 For example, to include extra packages:
 \"\\\\usepackage{foo}\\n\\\\usepackage{bar}\\n\"."
-  :type 'string
+  :type '(choice (const nil) string)
   :group 'calendar-tex
   :version "22.1")