Why are my GtkEntry icon tooltips not working?

Question

I have define a GtkEntry in GJS like so:

let myEntry = new Gtk.Entry({
    hexpand: true,
    placeholder_text: "Type here...",
    secondary_icon_name: "dialog-error-symbolic",
    secondary_icon_tooltip_text: "Send...",
    secondary_icon_activatable: true,
    secondary_icon_sensitive: true
});

However, the tooltip never shows. No error is printed to log and I've combed the docs for properties and functions, am I missing something?

UPDATE

This is a known bug in get_icon_at_pos() which is used by the ::query-tooltip handler and a fix has been pushed upstream by Daniel Boles on 2017-07-31.