Creating new window with custom menus

I am trying to create a new window with some custom menus in version 5.3. I can't seem to get the custom menus to appear. I am doing:

local win = window_create('edit', 1+2+8+16, -1, "400x500-20+20")
current_window(win)
menu_add -menu . CustomMenu
window_show(win, 1)

According to the help, the "2" in the window_create flag is to add a menu_bar. Not sure what I am doing wrong.

Thanks in advance.