dbus.call or dbus.propery.get inside awesome

[vercapi]

Following code doesn't work inside awesome.

local batter_opts = {bus = 'system',
                    path='/org/freedesktop/UPower',
                    interface="/org/freedesktop/UPower/devices/battery_BAT1",
                    destination='org.freedesktop.UPower'}
dbus.property.get("OnBattery", function(...)
                     print("callback is success")
                               end, batter_opts)
print("call is success")

On stdout I can see "call is success" but I never see "callback is success".

When I execute this code in vanilla lua (and the code from the reamde) it works as expected.

Can you help me out here? Are there some special things that need to be setup for awesome to work? Thanks.

Btw: dbus.on does work fine...