PaperMC/paper-server/patches/sources/net/minecraft/world/level/LevelWriter.java.patch

--- a/net/minecraft/world/level/LevelWriter.java
+++ b/net/minecraft/world/level/LevelWriter.java
@@ -28,4 +28,10 @@
     default boolean addFreshEntity(Entity entity) {
         return false;
     }
+
+    // CraftBukkit start
+    default boolean addFreshEntity(Entity entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
+        return false;
+    }
+    // CraftBukkit end
 }