diff --git a/src/main/java/com/comphenix/protocol/utility/StreamSerializer.java b/src/main/java/com/comphenix/protocol/utility/StreamSerializer.java
index 0d1f4de24..e6a5ae967 100644
--- a/src/main/java/com/comphenix/protocol/utility/StreamSerializer.java
+++ b/src/main/java/com/comphenix/protocol/utility/StreamSerializer.java
@@ -10,7 +10,9 @@
 import com.comphenix.protocol.injector.netty.NettyByteBufAdapter;
 import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.reflect.accessors.Accessors;
+import com.comphenix.protocol.reflect.accessors.FieldAccessor;
 import com.comphenix.protocol.reflect.accessors.MethodAccessor;
+import com.comphenix.protocol.reflect.fuzzy.FuzzyFieldContract;
 import com.comphenix.protocol.reflect.fuzzy.FuzzyMethodContract;
 import com.comphenix.protocol.wrappers.nbt.NbtCompound;
 import com.comphenix.protocol.wrappers.nbt.NbtFactory;
@@ -31,6 +33,7 @@ public class StreamSerializer {
     private static final StreamSerializer DEFAULT = new StreamSerializer();
 
     // Cached methods
+    private static FieldAccessor STREAM_CODEC;
     private static MethodAccessor READ_ITEM_METHOD;
     private static MethodAccessor WRITE_ITEM_METHOD;
 
@@ -235,14 +238,35 @@ public ItemStack deserializeItemStackFromByteArray(byte[] input) {
         Object serializer = MinecraftReflection.getPacketDataSerializer(buf);
 
         if (READ_ITEM_METHOD == null) {
-            READ_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection
-                    .fromClass(serializer.getClass(), false)
-                    .getMethodByReturnTypeAndParameters("readItemStack", MinecraftReflection.getItemStackClass()));
+            if (MinecraftVersion.v1_21_0.atOrAbove()) {
+                if (STREAM_CODEC == null) {
+                    STREAM_CODEC = Accessors.getFieldAccessor(FuzzyReflection
+                            .fromClass(MinecraftReflection.getItemStackClass())
+                            .getFieldList(FuzzyFieldContract.newBuilder()
+                                    .typeExact(MinecraftReflection.getStreamCodecClass())
+                                    .build()).get(1)); //skip OPTIONAL_STREAM_CODEC
+                }
+
+                READ_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection.fromObject(STREAM_CODEC.get(null), true)
+                        .getMethod(FuzzyMethodContract.newBuilder()
+                                .parameterExactType(MinecraftReflection.getRegistryFriendlyByteBufClass().get())
+                                .returnTypeExact(MinecraftReflection.getItemStackClass())
+                                .build()));
+            } else {
+                READ_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection
+                        .fromClass(serializer.getClass(), false)
+                        .getMethodByReturnTypeAndParameters("readItemStack", MinecraftReflection.getItemStackClass()));
+            }
         }
 
         try {
             // unwrap the item
-            Object nmsItem = READ_ITEM_METHOD.invoke(serializer);
+            Object nmsItem;
+            if (MinecraftVersion.v1_21_0.atOrAbove()) {
+                nmsItem = READ_ITEM_METHOD.invoke(STREAM_CODEC.get(null), serializer);
+            } else {
+                nmsItem = READ_ITEM_METHOD.invoke(serializer);
+            }
             return nmsItem != null ? MinecraftReflection.getBukkitItemStack(nmsItem) : null;
         } finally {
             ReferenceCountUtil.safeRelease(buf);
@@ -262,11 +286,26 @@ public ItemStack deserializeItemStackFromByteArray(byte[] input) {
      * @throws IOException If the operation fails due to reflection problems.
      */
     public void serializeItemStack(DataOutputStream output, ItemStack stack) throws IOException {
-        // TODO this functionality was replaced by the CODEC field in the nms ItemStack
         if (WRITE_ITEM_METHOD == null) {
-            WRITE_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection
-                    .fromClass(MinecraftReflection.getPacketDataSerializerClass(), true)
-                    .getMethodByParameters("writeStack", MinecraftReflection.getItemStackClass()));
+            if (MinecraftVersion.v1_21_0.atOrAbove()) {
+                if (STREAM_CODEC == null) {
+                    STREAM_CODEC = Accessors.getFieldAccessor(FuzzyReflection
+                            .fromClass(MinecraftReflection.getItemStackClass())
+                            .getFieldList(FuzzyFieldContract.newBuilder()
+                                    .typeExact(MinecraftReflection.getStreamCodecClass())
+                                    .build()).get(1)); //skip OPTIONAL_STREAM_CODEC
+                }
+
+                WRITE_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection.fromObject(STREAM_CODEC.get(null), true)
+                        .getMethod(FuzzyMethodContract.newBuilder()
+                                .parameterExactArray(MinecraftReflection.getRegistryFriendlyByteBufClass().get(), MinecraftReflection.getItemStackClass())
+                                .returnTypeExact(void.class)
+                                .build()));
+            } else {
+                WRITE_ITEM_METHOD = Accessors.getMethodAccessor(FuzzyReflection
+                        .fromClass(MinecraftReflection.getPacketDataSerializerClass(), true)
+                        .getMethodByParameters("writeStack", MinecraftReflection.getItemStackClass()));
+            }
         }
 
         ByteBuf buf = Unpooled.buffer();
@@ -274,7 +313,12 @@ public void serializeItemStack(DataOutputStream output, ItemStack stack) throws
 
         // Get the NMS version of the ItemStack and write it into the buffer
         Object nmsItem = MinecraftReflection.getMinecraftItemStack(stack);
-        WRITE_ITEM_METHOD.invoke(serializer, nmsItem);
+
+        if (MinecraftVersion.v1_21_0.atOrAbove()) {
+            WRITE_ITEM_METHOD.invoke(STREAM_CODEC.get(null), serializer, nmsItem);
+        } else {
+            WRITE_ITEM_METHOD.invoke(serializer, nmsItem);
+        }
 
         // write the serialized content to the stream
         output.write(this.getBytesAndRelease(buf));
diff --git a/src/test/java/com/comphenix/protocol/utility/StreamSerializerTest.java b/src/test/java/com/comphenix/protocol/utility/StreamSerializerTest.java
index 1d73f7c24..301ad6877 100644
--- a/src/test/java/com/comphenix/protocol/utility/StreamSerializerTest.java
+++ b/src/test/java/com/comphenix/protocol/utility/StreamSerializerTest.java
@@ -60,7 +60,6 @@ public void testCompound() throws IOException {
     }
 
     @Test
-    @Disabled // TODO -- replaced with registry friendly bytebuf
     public void testItems() throws IOException {
         StreamSerializer serializer = new StreamSerializer();
         ItemStack initial = new ItemStack(Material.STRING);
@@ -72,7 +71,6 @@ public void testItems() throws IOException {
     }
 
     @Test
-    @Disabled // TODO -- replaced with registry friendly bytebuf
     public void testItemMeta() throws IOException {
         StreamSerializer serializer = new StreamSerializer();
         ItemStack initial = new ItemStack(Material.BLUE_WOOL, 2);