--- a/net/minecraft/server/WorldGenRegistration.java
+++ b/net/minecraft/server/WorldGenRegistration.java
@@ -157,7 +157,7 @@
                         entitywitch.cU();
                         entitywitch.setPositionRotation((double) i + 0.5D, (double) j, (double) k + 0.5D, 0.0F, 0.0F);
                         entitywitch.prepare(world.D(new BlockPosition(i, j, k)), (GroupDataEntity) null);
-                        world.addEntity(entitywitch);
+                        world.addEntity(entitywitch, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.CHUNK_GEN); // CraftBukkit - add SpawnReason
                     }
                 }