~OnKill doesnt trigger

When a Crucible item runs a projectile or raytrace skill, when that skill deals damage and kills a mob, that kill will not trigger ~onKill

  - raytrace{entitySkill=CustomWeaponAttack;raywidth=0.2;maxdistance=3} ~onSwing
  - message{m="A mob was slain"} @Server ~onKill

CustomWeaponAttack:
  Skills:
  - damage{amount=20;element=PHYSICAL;preventimmunity=true;ignorearmor=true}

Even though the weapon runs this skill and kills the mob with the effect, the onkill message will never run. The same thing happens with projectile skills as well.