diff --git a/src/client.js b/src/client.js
index 472a777..e3af1d0 100644
--- a/src/client.js
+++ b/src/client.js
@@ -62,7 +62,8 @@ class Client extends Connection {
       const mcData = require('minecraft-data')('bedrock_' + this.options.version)
       this.features = {
         compressorInHeader: mcData.supportFeature('compressorInPacketHeader'),
-        itemRegistryPacket: mcData.supportFeature('itemRegistryPacket')
+        itemRegistryPacket: mcData.supportFeature('itemRegistryPacket'),
+        newLoginIdentityFields: mcData.supportFeature('newLoginIdentityFields')
       }
     } catch (e) {
       throw new Error(`Unsupported version: '${this.options.version}', no data available`)
@@ -146,9 +147,18 @@ class Client extends Connection {
       ...this.accessToken // Mojang + Xbox JWT from auth
     ]
 
-    const encodedChain = JSON.stringify({ chain })
-
-    debug('Auth chain', chain)
+    let encodedChain
+    if (this.features.newLoginIdentityFields) { // 1.21.90+
+      encodedChain = JSON.stringify({
+        Certificate: JSON.stringify({ chain }),
+        // 0 = normal, 1 = ss, 2 = offline
+        AuthenticationType: this.options.offline ? 2 : 0,
+        Token: ''
+      })
+    } else {
+      encodedChain = JSON.stringify({ chain })
+    }
+    debug('Auth chain', encodedChain)
 
     this.write('login', {
       protocol_version: this.options.protocolVersion,
diff --git a/src/server.js b/src/server.js
index 0f51bae..0b43fd2 100644
--- a/src/server.js
+++ b/src/server.js
@@ -33,7 +33,8 @@ class Server extends EventEmitter {
     try {
       const mcData = require('minecraft-data')('bedrock_' + version)
       this.features = {
-        compressorInHeader: mcData.supportFeature('compressorInPacketHeader')
+        compressorInHeader: mcData.supportFeature('compressorInPacketHeader'),
+        newLoginIdentityFields: mcData.supportFeature('newLoginIdentityFields')
       }
     } catch (e) {
       throw new Error(`Unsupported version: '${version}', no data available`)
diff --git a/src/serverPlayer.js b/src/serverPlayer.js
index b7ef02d..2e8ea77 100644
--- a/src/serverPlayer.js
+++ b/src/serverPlayer.js
@@ -78,11 +78,18 @@ class Player extends Connection {
 
     // Parse login data
     const tokens = body.params.tokens
-    const authChain = JSON.parse(tokens.identity)
-    const skinChain = tokens.client
-
     try {
-      var { key, userData, skinData } = this.decodeLoginJWT(authChain.chain, skinChain) // eslint-disable-line
+      const skinChain = tokens.client
+      const authChain = JSON.parse(tokens.identity)
+      let chain
+      if (authChain.Certificate) { // 1.21.90+
+        chain = JSON.parse(authChain.Certificate).chain
+      } else if (authChain.chain) {
+        chain = authChain.chain
+      } else {
+        throw new Error('Invalid login packet: missing chain or Certificate')
+      }
+      var { key, userData, skinData } = this.decodeLoginJWT(chain, skinChain) // eslint-disable-line
     } catch (e) {
       debug(this.address, e)
       this.disconnect('Server authentication error')
diff --git a/tools/compileProtocol.js b/tools/compileProtocol.js
index dcf6545..a7c3aa0 100644
--- a/tools/compileProtocol.js
+++ b/tools/compileProtocol.js
@@ -15,7 +15,6 @@ function createProtocol (version) {
   const compiler = new ProtoDefCompiler()
   const protocol = mcData('bedrock_' + version).protocol.types
   compiler.addTypes(require('../src/datatypes/compiler-minecraft'))
-  compiler.addTypes(require('prismarine-nbt/zigzag').compiler)
   compiler.addTypesToCompile(protocol)
 
   fs.writeFileSync('./read.js', 'module.exports = ' + compiler.readCompiler.generate().replace('() =>', 'native =>'))
@@ -39,7 +38,7 @@ require('minecraft-data/bin/generate_data')
 
 // If no argument, build everything
 if (!process.argv[2]) {
-  convert('latest')
+  convert('bedrock', 'latest')
   for (const version of versions) {
     main(version)
   }