On Wither Skull hit add effects to player

I'm having quite a problem here (Which you can probably solve in a few seconds... What can I do, I'm a noob) - I want to add a wither effect to a player on wither skull hit. I know that the player gets the effect when a Wither hits you with it's skull, but I've made a "Wither Skull Bow" and it just doesn't give the effects. My code so far:

Code:

public void skullHit(EntityDamageByEntityEvent e) {
      Player victim = (Player) e.getEntity();
      if(victim instanceof Player) {
      if(e.getDamager() instanceof WitherSkull) {
        victim.addPotionEffect(new PotionEffect(PotionEffectType.WITHER, 0, 10));
        }
      }
    }

 

new PotionEffect(PotionEffectType.WITHER, DURATION!, MODIFIER)
try changing it to this.

Code:

public void skullHit(EntityDamageByEntityEvent e) {
if(e.getEntity() instanceof Player) { //needed
Player victim = (Player) e.getEntity();
if(e.getDamager() instanceof WitherSkull) {
victim.addPotionEffect(new PotionEffect(PotionEffectType.WITHER, 10, 1));
}
}
}

you had the duration of the potion effect set to zero meaning the effect wont occur.
your modifier was also set to 10 meaning the effects would be ultimate.