--- a/net/minecraft/world/effect/InfestedMobEffect.java
+++ b/net/minecraft/world/effect/InfestedMobEffect.java
@@ -48,7 +48,11 @@
 
             entitysilverfish.moveTo(d0, d1, d2, worldserver.getRandom().nextFloat() * 360.0F, 0.0F);
             entitysilverfish.setDeltaMovement(new Vec3D(vector3f));
-            worldserver.addFreshEntity(entitysilverfish);
+            // CraftBukkit start
+            if (!worldserver.addFreshEntity(entitysilverfish, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.POTION_EFFECT)) {
+                return;
+            }
+            // CraftBukkit end
             entitysilverfish.playSound(SoundEffects.SILVERFISH_HURT);
         }
     }
