diff --git a/src/datatypes/minecraft.js b/src/datatypes/minecraft.js
index d7625c1..a366468 100644
--- a/src/datatypes/minecraft.js
+++ b/src/datatypes/minecraft.js
@@ -1,11 +1,12 @@
 const nbt = require('prismarine-nbt');
 const UUID = require('uuid-1345');
+const zlib = require('zlib');
 
 module.exports = {
   'UUID': [readUUID, writeUUID, 16],
   'nbt': [readNbt, writeNbt, sizeOfNbt],
   'optionalNbt':[readOptionalNbt,writeOptionalNbt,sizeOfOptionalNbt],
-  'optionalLengthPrefixedNbt':[readOptionalLengthPrefixedNbt,writeOptionalLengthPrefixedNbt,sizeOfOptionalLengthPrefixedNbt],
+  'compressedNbt':[readCompressedNbt,writeCompressedNbt,sizeOfCompressedNbt],
   'restBuffer': [readRestBuffer, writeRestBuffer, sizeOfRestBuffer],
   'entityMetadataLoop': [readEntityMetadata, writeEntityMetadata, sizeOfEntityMetadata]
 };
@@ -55,13 +56,19 @@ function sizeOfOptionalNbt(value) {
   return nbt.proto.sizeOf(value,"nbt");
 }
 
-// Length-prefixed optional NBT, short instead of null byte: http://wiki.vg/index.php?title=Slot_Data&diff=6056&oldid=4753
-function readOptionalLengthPrefixedNbt(buffer, offset) {
-  if(buffer.readInt16BE(offset) == -1) return {size:2};
-  return nbt.proto.read(buffer,offset+2,"nbt");
+// Length-prefixed compressed NBT, see differences: http://wiki.vg/index.php?title=Slot_Data&diff=6056&oldid=4753
+function readCompressedNbt(buffer, offset) {
+  const length = buffer.readInt16BE(offset);
+  if(length == -1) return {size:2};
+
+  const compressedNbt = buffer.slice(offset+2, offset+2+length);
+
+  const nbtBuffer = zlib.gunzipSync(compressedNbt); // TODO: async
+
+  return nbt.proto.read(nbtBuffer,0,"nbt");
 }
 
-function writeOptionalLengthPrefixedNbt(value, buffer, offset) {
+function writeCompressedNbt(value, buffer, offset) {
   if(value==undefined) {
     buffer.writeInt16BE(-1,offset);
     return offset+2;
@@ -70,7 +77,7 @@ function writeOptionalLengthPrefixedNbt(value, buffer, offset) {
   return nbt.proto.write(value,buffer,offset+2,"nbt");
 }
 
-function sizeOfOptionalLengthPrefixedNbt(value) {
+function sizeOfCompressedNbt(value) {
   if(value==undefined)
     return 2;
   return 2+nbt.proto.sizeOf(value,"nbt");