(ex-unix-type-shell-options): Fix :type.

diff --git a/lisp/emulation/viper-ex.el b/lisp/emulation/viper-ex.el
index 48b99bc3871ca5a967fc27bb26bbf79b305da249..9a7439a6309f355124ec7956536ac14f2581984d 100644 (file)
--- a/lisp/emulation/viper-ex.el
+++ b/lisp/emulation/viper-ex.el
@@ -166,7 +166,7 @@
              )))
   "Options to pass to the Unix-style shell. 
 Don't put `-c' here, as it is added automatically."
-  :type 'string
+  :type '(choice (const nil) string)
   :group 'viper-ex)
 
 (defcustom viper-glob-function