diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 04c38b2..e73a9da 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8054,6 +8054,23 @@
 	Note that the "cterm" attributes are still used, not the "gui" ones.
 	NOTE: This option is reset when 'compatible' is set.
 
+						*'termmode'* *'tmod'*
+'termmode' 'tmod'	string  (default "")
+			local to window
+			{not in Vi, MS-Windows only}
+	Whether the window uses winpty or |ConPTY| as the virtual console.
+	When set before opening the terminal, it influences what pty is used.
+	When opening the terminal it will be set to the actually used pty.
+
+	Possible values are:
+	    ""		use ConPTY if possible, winpty otherwise
+	    "winpty"	use winpty, fail if not supported
+	    "conpty"	use |ConPTY|, fail if not supported
+
+	|ConPTY| support depends on the platform (Windows 10 October 2018
+	edition).  winpty support needs to be installed.  If neither is
+	supported then you cannot open a terminal window.
+
 						*'termwinscroll'* *'twsl'*
 'termwinscroll' 'twsl'	number	(default 10000)
 			local to buffer