Gtk3 FileChooser Bug?

#!/usr/bin/env python
import os
import sys
from gi.repository import Gtk

#
# Make sure you point TARGET_DIR to an empty directory
# file_one.txt will be successfully created.
# When second dialog opens it will have file_one.txt in the
# input field instead of file_two.txt as set with set_current_filename()
#

TARGET_DIR="~/Videos"

class app(Gtk.Window):
  def __init__(self):
    Gtk.Window.__init__(self, title="Testink, testink, ...")
    self.show_all()

    (foo, bar) = self.dialog("First", "file_one.txt")

    if bar == Gtk.ResponseType.OK:
      folder = foo.get_current_folder()
      fn = foo.get_filename()
      print "FOL", folder, "FN", fn
      filepath = os.path.join(foo.get_current_folder(),
                              foo.get_filename())
      f = open(filepath, "w+")
      f.write("BigW Was Here\n")
      f.close()
    foo.destroy()

    (foo, bar) = self.dialog("Second", "file_two.txt")

    if bar == Gtk.ResponseType.OK:
      filepath = os.path.join(foo.get_current_folder(),
                              foo.get_filename())
      f = open(filepath, "w+")
      f.write("BigW Was Here, for the second time!\n")
      f.close()
    foo.destroy()

  def dialog(self, title, filename):
    dlg = Gtk.FileChooserDialog(title, None, Gtk.FileChooserAction.SAVE,
                                (Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL,
                                "Save", Gtk.ResponseType.OK))

    dlg.set_current_name(filename)
    dlg.set_do_overwrite_confirmation(True)
    path = os.path.expanduser(TARGET_DIR)
    dlg.set_current_folder(path)
    dlg.show_all()
    result = dlg.run()
    return dlg, result

ap = app()
ap.show_all()
ap.connect("delete-event", Gtk.main_quit)
Gtk.main()