--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4792,10 +4792,22 @@ A jump table for the options with a shor
 	completion with CTRL-X CTRL-O. |i_CTRL-X_CTRL-O|
 	See |complete-functions| for an explanation of how the function is
 	invoked and what it should return.
-	This option is usually set by a filetype plugin.
+	This option is usually set by a filetype plugin:
 	|:filetype-plugin-on|
 
 
+				*'opendevice* *'odev* *'noopendevice* *'noodev*
+'opendevice' 'odev'	boolean	(default off)
+			global
+			{not in Vi}
+			{only for MS-DOS, MS-Windows and OS/2}
+	Enable reading and writing from devices.  This may get Vim stuck on a
+	device that can be opened but doesn't actually do the I/O.  Therefore
+	it is off by default.
+	Note that on MS-Windows editing "aux.h", "lpt1.txt" and the like also
+	result in editing a device.
+
+
 						*'operatorfunc'* *'opfunc'*
 'operatorfunc' 'opfunc'	string	(default: empty)
 			global