diff --git a/pom.xml b/pom.xml
index d4e5f7ac..c8476c29 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
 
     <groupId>com.github.steveice10</groupId>
     <artifactId>mcprotocollib</artifactId>
-    <version>1.16.4-SNAPSHOT</version>
+    <version>20w45a-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>MCProtocolLib</name>
diff --git a/src/main/java/com/github/steveice10/mc/protocol/MinecraftConstants.java b/src/main/java/com/github/steveice10/mc/protocol/MinecraftConstants.java
index 3c2655eb..d70cdf44 100644
--- a/src/main/java/com/github/steveice10/mc/protocol/MinecraftConstants.java
+++ b/src/main/java/com/github/steveice10/mc/protocol/MinecraftConstants.java
@@ -12,12 +12,12 @@ public final class MinecraftConstants {
     /**
      * Current supported game version.
      */
-    public static final String GAME_VERSION = "1.16.4";
+    public static final String GAME_VERSION = "20w45a";
 
     /**
      * Current supported protocol version.
      */
-    public static final int PROTOCOL_VERSION = 754;
+    public static final int PROTOCOL_VERSION = (1 << 30) | 5;
 
     // General Key Constants
 
diff --git a/src/main/java/com/github/steveice10/mc/protocol/data/game/chunk/Column.java b/src/main/java/com/github/steveice10/mc/protocol/data/game/chunk/Column.java
index 1313f889..8a945cfa 100644
--- a/src/main/java/com/github/steveice10/mc/protocol/data/game/chunk/Column.java
+++ b/src/main/java/com/github/steveice10/mc/protocol/data/game/chunk/Column.java
@@ -13,13 +13,13 @@ public class Column {
     private final @NonNull Chunk[] chunks;
     private final @NonNull CompoundTag[] tileEntities;
     private final @NonNull CompoundTag heightMaps;
-    private final int[] biomeData;
+    private final @NonNull int[] biomeData;
 
     public Column(int x, int z, @NonNull Chunk[] chunks, @NonNull CompoundTag[] tileEntities, @NonNull CompoundTag heightMaps) {
-        this(x, z, chunks, tileEntities, heightMaps, null);
+        this(x, z, chunks, tileEntities, heightMaps, new int[0]);
     }
 
-    public Column(int x, int z, @NonNull Chunk[] chunks, @NonNull CompoundTag[] tileEntities, @NonNull CompoundTag heightMaps, int[] biomeData) {
+    public Column(int x, int z, @NonNull Chunk[] chunks, @NonNull CompoundTag[] tileEntities, @NonNull CompoundTag heightMaps, @NonNull int[] biomeData) {
         if(chunks.length != 16) {
             throw new IllegalArgumentException("Chunk array length must be 16.");
         }
diff --git a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/ServerResourcePackSendPacket.java b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/ServerResourcePackSendPacket.java
index 8f45ab2d..674518a6 100644
--- a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/ServerResourcePackSendPacket.java
+++ b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/ServerResourcePackSendPacket.java
@@ -19,17 +19,20 @@ import java.io.IOException;
 public class ServerResourcePackSendPacket implements Packet {
     private @NonNull String url;
     private @NonNull String hash;
+    private boolean mustAcceptPack;
 
     @Override
     public void read(NetInput in) throws IOException {
         this.url = in.readString();
         this.hash = in.readString();
+        this.mustAcceptPack = in.readBoolean();
     }
 
     @Override
     public void write(NetOutput out) throws IOException {
         out.writeString(this.url);
         out.writeString(this.hash);
+        out.writeBoolean(this.mustAcceptPack);
     }
 
     @Override
diff --git a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerChunkDataPacket.java b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerChunkDataPacket.java
index e45cbbe2..1d59bb5f 100644
--- a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerChunkDataPacket.java
+++ b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerChunkDataPacket.java
@@ -31,14 +31,11 @@ public class ServerChunkDataPacket implements Packet {
     public void read(NetInput in) throws IOException {
         int x = in.readInt();
         int z = in.readInt();
-        boolean fullChunk = in.readBoolean();
         int chunkMask = in.readVarInt();
         CompoundTag heightMaps = NBT.read(in);
-        int[] biomeData = fullChunk ? new int[in.readVarInt()] : null;
-        if (fullChunk) {
-            for (int index = 0; index < biomeData.length; index++) {
-                biomeData[index] = in.readVarInt();
-            }
+        int[] biomeData = new int[in.readVarInt()];
+        for (int index = 0; index < biomeData.length; index++) {
+            biomeData[index] = in.readVarInt();
         }
         byte[] data = in.readBytes(in.readVarInt());
 
@@ -73,18 +70,13 @@ public class ServerChunkDataPacket implements Packet {
             }
         }
 
-        boolean fullChunk = this.column.getBiomeData() != null;
-
         out.writeInt(this.column.getX());
         out.writeInt(this.column.getZ());
-        out.writeBoolean(fullChunk);
         out.writeVarInt(mask);
         NBT.write(out, this.column.getHeightMaps());
-        if (fullChunk) {
-            out.writeVarInt(this.column.getBiomeData().length);
-            for (int biomeData : this.column.getBiomeData()) {
-                out.writeVarInt(biomeData);
-            }
+        out.writeVarInt(this.column.getBiomeData().length);
+        for (int biomeData : this.column.getBiomeData()) {
+            out.writeVarInt(biomeData);
         }
         out.writeVarInt(dataBytes.size());
         out.writeBytes(dataBytes.toByteArray(), dataBytes.size());
diff --git a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerUpdateLightPacket.java b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerUpdateLightPacket.java
index 1e644d72..8a97eb66 100644
--- a/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerUpdateLightPacket.java
+++ b/src/main/java/com/github/steveice10/mc/protocol/packet/ingame/server/world/ServerUpdateLightPacket.java
@@ -49,10 +49,10 @@ public class ServerUpdateLightPacket implements Packet {
         this.z = in.readVarInt();
         this.trustEdges = in.readBoolean();
 
-        int skyLightMask = in.readVarInt();
-        int blockLightMask = in.readVarInt();
-        int emptySkyLightMask = in.readVarInt();
-        int emptyBlockLightMask = in.readVarInt();
+        long skyLightMask = in.readVarLong();
+        long blockLightMask = in.readVarLong();
+        long emptySkyLightMask = in.readVarLong();
+        long emptyBlockLightMask = in.readVarLong();
 
         this.skyLight = new NibbleArray3d[NUM_ENTRIES];
         for (int i = 0; i < NUM_ENTRIES; i++) {
@@ -108,10 +108,10 @@ public class ServerUpdateLightPacket implements Packet {
             }
         }
 
-        out.writeVarInt(skyLightMask);
-        out.writeVarInt(blockLightMask);
-        out.writeVarInt(emptySkyLightMask);
-        out.writeVarInt(emptyBlockLightMask);
+        out.writeVarLong(skyLightMask);
+        out.writeVarLong(blockLightMask);
+        out.writeVarLong(emptySkyLightMask);
+        out.writeVarLong(emptyBlockLightMask);
 
         for(int i = 0; i < NUM_ENTRIES; i++) {
             if((skyLightMask & 1 << i) != 0) {