From c8802f0a64036c0dd368a0e9fea36809e6ab2a04 Mon Sep 17 00:00:00 2001
From: CraftBukkit/Spigot <noreply+git-craftbukkit@papermc.io>
Date: Tue, 23 Nov 2021 20:00:10 +1100
Subject: [PATCH] Fix upgrading worlds with custom generators

By: md_5 <git@md-5.net>
---
 .../org/bukkit/craftbukkit/generator/CustomChunkGenerator.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java b/paper-server/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
index 9ce28303b5..6a5d231065 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
@@ -306,6 +306,6 @@ public class CustomChunkGenerator extends InternalChunkGenerator {
 
     @Override
     protected Codec<? extends net.minecraft.world.level.chunk.ChunkGenerator> codec() {
-        throw new UnsupportedOperationException("Cannot serialize CustomChunkGenerator");
+        return Codec.unit(null);
     }
 }