[SIP Beyond VoIP] sipclients alert_device setting does not work

[Juha Heinanen]

i have usb audio device that works fine as input/output device.  also
setting that device as alert_device succeeds:

jh at siika:~/test$ sip-settings --general set audio.alert_device=usb
using set_wakeup_fd
SIP SIMPLE general settings updated
jh at siika:~/test$ sip-settings --general show
using set_wakeup_fd
SIP SIMPLE settings:
...
        +-- alert_device = usb
audio --|-- directory = UserDataPath(u'history')
        |-- input_device = usb
        |-- output_device = usb
        |-- sample_rate = 44100
        |-- silent = False
        +-- tail_length = 100

however, when i make a call with sip-audio-session, it starts to look
for system default device, which is not at the moment available.  this
results in a long delay in call setup and after the call, alert_device
has magically changed back to system_default:

$ sip-audio-session sip:4444 at sip2sip.info
using set_wakeup_fd
Using account jh at test.fi
Available audio input devices: None, system_default, /dev/dsp, /dev/dsp2, Generic USB Audio Device: USB Audio (hw:2,0), HDA ATI SB: STAC92xx Analog (hw:0,0), internal, sysdefault, usb
Available audio output devices: None, system_default, /dev/dsp, /dev/dsp2, Generic USB Audio Device: USB Audio (hw:2,0), HD-Audio Generic: HDMI 0 (hw:1,3), HDA ATI SB: STAC92xx Analog (hw:0,0), dmix, dmixer, front, hdm, internal, surround40, surround51, surround71, sysdefault, usb
Using audio input device: usb
Using audio output device: usb
Using audio alert device: HDA ATI SB: STAC92xx Analog (hw:0,0) (system default device)
...
$ sip-settings --general show
SIP SIMPLE settings:
...
        +-- alert_device = system_default
audio --|-- directory = UserDataPath(u'history')
        |-- input_device = usb
        |-- output_device = usb
        |-- sample_rate = 44100
        |-- silent = False
        +-- tail_length = 100

is there a bug in usage of configured alert_device or is there some
other explanation to the above described behavior?

-- juha