diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index de7f197..54e5e29 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1021,6 +1021,7 @@
 	test_garbagecollect_now()   free memory right now
 	test_garbagecollect_soon()  set a flag to free memory soon
 	test_getvalue()		get value of an internal variable
+	test_gui_drop_files()	drop file(s) in a window
 	test_gui_mouse_event()	add a GUI mouse event to the input buffer
 	test_ignore_error()	ignore a specific error message
 	test_null_blob()	return a null Blob