--- a/net/minecraft/util/worldupdate/WorldUpgrader.java
+++ b/net/minecraft/util/worldupdate/WorldUpgrader.java
@@ -82,7 +82,7 @@
 
     public WorldUpgrader(Convertable.ConversionSession convertable_conversionsession, DataFixer datafixer, SaveData savedata, IRegistryCustom iregistrycustom, boolean flag, boolean flag1) {
         this.dimensions = iregistrycustom.lookupOrThrow(Registries.LEVEL_STEM);
-        this.levels = (Set) this.dimensions.registryKeySet().stream().map(Registries::levelStemToLevel).collect(Collectors.toUnmodifiableSet());
+        this.levels = (Set) java.util.stream.Stream.of(convertable_conversionsession.dimensionType).map(Registries::levelStemToLevel).collect(Collectors.toUnmodifiableSet()); // CraftBukkit
         this.eraseCache = flag;
         this.dataFixer = datafixer;
         this.levelStorage = convertable_conversionsession;
@@ -446,9 +446,9 @@
             if (nbttagcompound != null) {
                 int i = IChunkLoader.getVersion(nbttagcompound);
                 ChunkGenerator chunkgenerator = ((WorldDimension) WorldUpgrader.this.dimensions.getValueOrThrow(Registries.levelToLevelStem(resourcekey))).generator();
-                NBTTagCompound nbttagcompound1 = ichunkloader.upgradeChunkTag(resourcekey, () -> {
+                NBTTagCompound nbttagcompound1 = ichunkloader.upgradeChunkTag(Registries.levelToLevelStem(resourcekey), () -> { // CraftBukkit
                     return WorldUpgrader.this.overworldDataStorage;
-                }, nbttagcompound, chunkgenerator.getTypeNameForDataFixer());
+                }, nbttagcompound, chunkgenerator.getTypeNameForDataFixer(), chunkcoordintpair, null); // CraftBukkit
                 ChunkCoordIntPair chunkcoordintpair1 = new ChunkCoordIntPair(nbttagcompound1.getIntOr("xPos", 0), nbttagcompound1.getIntOr("zPos", 0));
 
                 if (!chunkcoordintpair1.equals(chunkcoordintpair)) {