--- a/net/minecraft/server/VillageSiege.java
+++ b/net/minecraft/server/VillageSiege.java
@@ -101,7 +101,7 @@
             }
 
             entityzombie.setPositionRotation(vec3d.x, vec3d.y, vec3d.z, this.a.random.nextFloat() * 360.0F, 0.0F);
-            this.a.addEntity(entityzombie);
+            this.a.addEntity(entityzombie, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.VILLAGE_INVASION); // CraftBukkit
         }
     }