PaperMC/paper-server/nms-patches/net/minecraft/world/entity/monster/EntityGuardianElder.patch

--- a/net/minecraft/world/entity/monster/EntityGuardianElder.java
+++ b/net/minecraft/world/entity/monster/EntityGuardianElder.java
@@ -67,7 +67,7 @@
         super.customServerAiStep();
         if ((this.tickCount + this.getId()) % 1200 == 0) {
             MobEffect mobeffect = new MobEffect(MobEffects.DIG_SLOWDOWN, 6000, 2);
-            List<EntityPlayer> list = MobEffectUtil.addEffectToPlayersAround((WorldServer) this.level(), this, this.position(), 50.0D, mobeffect, 1200);
+            List<EntityPlayer> list = MobEffectUtil.addEffectToPlayersAround((WorldServer) this.level(), this, this.position(), 50.0D, mobeffect, 1200, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.ATTACK); // CraftBukkit
 
             list.forEach((entityplayer) -> {
                 entityplayer.connection.send(new PacketPlayOutGameStateChange(PacketPlayOutGameStateChange.GUARDIAN_ELDER_EFFECT, this.isSilent() ? 0.0F : 1.0F));