Ability :MUMMY raises an error

[Hokath]

BattleHandlers::TargetAbilityOnHit.add(:MUMMY,
  proc { |ability,user,target,move,battle|
    next if !move.pbContactMove?(user)
    next if user.fainted?
    next if user.unstoppableAbility? || user.ability == ability
    oldAbil = -1
    battle.pbShowAbilitySplash(target) if user.opposes?(target)
    if user.affectedByContactEffect?(PokeBattle_SceneConstants::USE_ABILITY_SPLASH)
      oldAbil = user.ability
      battle.pbShowAbilitySplash(user,true,false) if user.opposes?(target)
      user.ability = ability
      battle.pbReplaceAbilitySplash(user) if user.opposes?(target)
      if PokeBattle_SceneConstants::USE_ABILITY_SPLASH
        battle.pbDisplay(_INTL("{1}'s Ability became {2}!",user.pbThis,user.abilityName))
      else
        battle.pbDisplay(_INTL("{1}'s Ability became {2} because of {3}!",
           user.pbThis,user.abilityName,target.pbThis(true)))
      end
      battle.pbHideAbilitySplash(user) if user.opposes?(target)
    end
    battle.pbHideAbilitySplash(target) if user.opposes?(target)
    user.pbOnAbilityChanged(oldAbil) if oldAbil>=0
  }
)

It doesn't like the last line.
I guess it used to refer to an ID which was a number, but not it is a symbol it doesn't like the >= logic?
(this won't crash the game once you dismiss the warning)