diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 7ff969d..05e8d70 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -666,6 +666,8 @@
 test_getvalue({string})		any	get value of an internal variable
 test_gui_event({event}, {args})	bool	generate a GUI event for testing
 test_ignore_error({expr})	none	ignore a specific error
+test_mswin_event({event}, {args})
+				bool	generate MS-Windows event for testing
 test_null_blob()		Blob	null value for testing
 test_null_channel()		Channel	null value for testing
 test_null_dict()		Dict	null value for testing