[ruby][то ли лыжи] Нотификации не срабатывают

#!/usr/bin/env ruby
# encoding: UTF-8
if RUBY_VERSION < '1.9'
    $KCODE = 'u'
end

require 'Qt4'

class Main_window < Qt::MainWindow
    def initialize(parent = nil)
        super
        init_dbus!
        init_tray_icon!
        show_message('Some test message here.')
        self
    end
    private
    def init_dbus!
        @bus = Qt::DBusConnection::session_bus
        unless @bus.connected?
            $stderr.puts 'No session bus found. Stopped.'
            exit(1)
        end
        @notify = Qt::DBusInterface.new(
            'org.freedesktop.Notifications',
            '/org/freedesktop/Notifications',
            'org.freedesktop.Notifications',
            @bus
        )
        unless @notify.valid?
            $stderr.puts 'Unable to found required D-Bus service. Stopped.'
            exit(2)
        end
        self
    end
    def init_tray_icon!
        @tray = Qt::SystemTrayIcon.new(self.style.standard_icon(Qt::Style::SP_MediaPlay), self)
        @tray.tool_tip = 'XMMS2 song change notifier'
        @menu = Qt::Menu.new(self)
        @action_quit = Qt::Action.new(self.style.standard_icon(Qt::Style::SP_DialogCloseButton), 'Quit', @menu)
        Qt::Object.connect(@action_quit, SIGNAL(:activated), self, SLOT(:close))
        @menu.add_action(@action_quit)
        @tray.context_menu = @menu
        @tray.visible = true
        self
    end
    def show_message(message)
        unless message.empty?
            $stdout.puts message
            @notify.call_with_argument_list(
                Qt::DBus::NoBlock,
                'Notify',
                [
                    'XMMS2 notify', Qt::Variant.fromValue(0, 'uint'),
                    'media-playback-start',
                    'Now playing', message,
                    [], {}, 5000
                ]
            )
        end
        self
    end
end

application = Qt::Application.new(ARGV)
main_window = Main_window.new
application.exec