Answering a call with i3-wm and dunst (Debian Stretch)

I'm using Ekiga 4.0.1 and can't answer incoming calls; if I click on the
popup window it disappears and there are not other notifications, e.g.
in the main window.
Screenshot: http://de.tinypic.com/r/29et8k1/9

Is there a workaround, e.g. answering the call with a hotkey?
(Automatically answering the call is not an option for me.)

I'm using the i3 window manager with the Dunst notification daemon on a
Debian Stretch.

Any help is appreciated.

Best,

Tom