Toggling visibility of widget is effective only after starting the Gtk loop

I would like to start a Gtk.jl window with two buttons, one of them being invisible; the visible button toggles the visibility of the invisible one.

I cannot set the visibility of the “invisible” button until after I start the Gtk main loop. Setting other properties, such as label before the main loop instead works as expected.

Is this a bug?

using Gtk

win = GtkWindow("Visible buttons")

b1 = GtkCheckButton("Click Me")
#set_gtk_property!(b1, :label, "Button 1")
b2 = GtkButton("This button disappears")
set_gtk_property!(b2, :visible, false)

signal_connect(b1, "clicked") do w
                      :visible, get_gtk_property(w, :active, Bool))

g = GtkGrid()
g[1,1] = b1
g[2,1] = b2

push!(win, g)
#set_gtk_property!(b2, :visible, false) # uncomment this to hide the button b2