~onSkillDamage does not work with items

TestSword:
  Id: DIAMOND_SWORD
  Skills:
  - damage{a=1000} @target ~onAttack
  - message{m="Test 2"} @self ~onSkillDamage

Using this item that I made for testing, the onSkillDamage trigger never activates. The damage is being properly applied, and the onSkillDamage trigger works with mobs, but not items.