Rimuovi l'asserzione da pmset

L'app Viber impedisce al display del mio Mac di spegnersi.

pmset -g                                                                                                                                                                         [2.2.0]
  Active Profiles:
  Battery Power     -1
  AC Power      -1*
  Currently in use:
    standbydelay         10800
    standby              1
    womp            

    1
    halfdim              1
    hibernatefile        /var/vm/sleepimage
    darkwakes            1
    gpuswitch            2
    networkoversleep     0
    disksleep            10
    sleep                5 (sleep prevented by AddressBookSour)
    autopoweroffdelay    14400
    hibernatemode        3
    autopoweroff         1
    ttyskeepawake        1
    displaysleep         5 (display sleep prevented by Viber)
    acwake               0
    lidwake              1


pmset -g assertions                                                                                                                                                              [2.2.0]
   2015-04-20 23:59:20 +0300
Assertion status system-wide:
   BackgroundTask                 0
   ApplePushServiceTask           0
   UserIsActive                   1
   PreventUserIdleDisplaySleep    1
   PreventSystemSleep             0
   ExternalMedia                  0
   PreventUserIdleSystemSleep     1
   NetworkClientActive            0
Listed by owning process:
   pid 78582(AddressBookSour): [0x000203b400010748] 00:00:06 PreventUserIdleSystemSleep named: "Address Book Source Sync"
    Timeout will fire in 1794 secs Action=TimeoutActionTurnOff
   pid 94(hidd): [0x0001fdc6000906c7] 00:25:24 UserIsActive named: "com.apple.iohideventsystem.queue.tickle"
    Timeout will fire in 285 secs Action=TimeoutActionRelease
   pid 827(Viber): [0x00015736000521d1] 12:16:02 NoDisplaySleepAssertion named: "Viber. Active call"
Kernel Assertions: 0x100=MAGICWAKE
   id=502  level=255 0x100=MAGICWAKE mod=4/19/15, 11:09 description=en0 owner=en0

Voglio avviare lo screensaver mentre Viber sta funzionando, quindi uccidere il pid di Viber non è un'opzione. Come rimuovere l'asserzione su Viber?