PaperMC/paper-server/nms-patches/net/minecraft/world/level/levelgen/MobSpawnerPhantom.patch

--- a/net/minecraft/world/level/levelgen/MobSpawnerPhantom.java
+++ b/net/minecraft/world/level/levelgen/MobSpawnerPhantom.java
@@ -74,7 +74,7 @@
                                                 if (entityphantom != null) {
                                                     entityphantom.moveTo(blockposition1, 0.0F, 0.0F);
                                                     groupdataentity = entityphantom.finalizeSpawn(worldserver, difficultydamagescaler, EnumMobSpawn.NATURAL, groupdataentity);
-                                                    worldserver.addFreshEntityWithPassengers(entityphantom);
+                                                    worldserver.addFreshEntityWithPassengers(entityphantom, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.NATURAL); // CraftBukkit
                                                     ++i;
                                                 }
                                             }