PaperMC/paper-server/patches/sources/net/minecraft/world/effect/PoisonMobEffect.patch

--- a/net/minecraft/world/effect/PoisonMobEffect.java
+++ b/net/minecraft/world/effect/PoisonMobEffect.java
@@ -14,7 +14,7 @@
     @Override
     public boolean applyEffectTick(WorldServer worldserver, EntityLiving entityliving, int i) {
         if (entityliving.getHealth() > 1.0F) {
-            entityliving.hurtServer(worldserver, entityliving.damageSources().magic(), 1.0F);
+            entityliving.hurtServer(worldserver, entityliving.damageSources().poison(), 1.0F);  // CraftBukkit - DamageSource.MAGIC -> CraftEventFactory.POISON
         }
 
         return true;