diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index d1a1ba3..bceb680 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1660,7 +1660,11 @@
 					*v:windowid* *windowid-variable*
 v:windowid	When any X11 based GUI is running or when running in a
 		terminal and Vim connects to the X server (|-X|) this will be
-		set to the window ID.  Otherwise the value is zero.
+		set to the window ID.
+		When an MS-Windows GUI is running this will be set to the
+		window handle.
+		Otherwise the value is zero.
+		Note: for windows inside Vim use |winnr()|.
 
 ==============================================================================
 4. Builtin Functions					*functions*