diff --git a/lib/websocket/frame.js b/lib/websocket/frame.js
index f9115fc6ecc..1df5e16934b 100644
--- a/lib/websocket/frame.js
+++ b/lib/websocket/frame.js
@@ -45,7 +45,8 @@ class WebsocketFrameSend {
     if (payloadLength === 126) {
       new DataView(buffer.buffer).setUint16(2, bodyLength)
     } else if (payloadLength === 127) {
-      // TODO: optimize this once tests are added for payloads >= 2^16 bytes
+      // Clear extended payload length
+      buffer[2] = buffer[3] = 0
       buffer.writeUIntBE(bodyLength, 4, 6)
     }
 
diff --git a/lib/websocket/receiver.js b/lib/websocket/receiver.js
index e532366d640..cd6e8bc4f7f 100644
--- a/lib/websocket/receiver.js
+++ b/lib/websocket/receiver.js
@@ -196,10 +196,10 @@ class ByteParser extends Writable {
       }
 
       const buffer = this.consume(8)
+      const upper = buffer.readUInt32BE(0)
+      const lower = buffer.readUInt32BE(4)
 
-      // TODO: optimize this
-      // TODO: this likely doesn't work because it returns a bigint
-      this.#info.payloadLength = buffer.readBigUint64BE(0)
+      this.#info.payloadLength = (upper << 8) + lower
       this.#state = parserStates.READ_DATA
     } else if (this.#state === parserStates.READ_DATA) {
       if (this.#byteOffset < this.#info.payloadLength) {
diff --git a/lib/websocket/websocket.js b/lib/websocket/websocket.js
index a5fa94f623d..3955b5664cf 100644
--- a/lib/websocket/websocket.js
+++ b/lib/websocket/websocket.js
@@ -314,7 +314,14 @@ class WebSocket extends EventTarget {
       // by the length of data’s buffer in bytes.
 
       const ab = new ArrayBuffer(data.byteLength)
-      new data.constructor(ab).set(data)
+
+      if (Buffer.isBuffer(data)) {
+        // new Buffer signature is deprecated
+        Buffer.from(ab).set(data)
+      } else {
+        new data.constructor(ab).set(data)
+      }
+
       const value = Buffer.from(ab)
 
       const frame = new WebsocketFrameSend(value)
diff --git a/test/websocket/send.js b/test/websocket/send.js
new file mode 100644
index 00000000000..3fa4b342bfe
--- /dev/null
+++ b/test/websocket/send.js
@@ -0,0 +1,35 @@
+'use strict'
+
+const { test } = require('tap')
+const { WebSocketServer } = require('ws')
+const { Blob } = require('buffer')
+const { WebSocket } = require('../..')
+
+test('Sending > 2^16 bytes', (t) => {
+  t.plan(3)
+
+  const server = new WebSocketServer({ port: 0 })
+
+  server.on('connection', (ws) => {
+    ws.on('message', (m, isBinary) => {
+      ws.send(m, { binary: isBinary })
+    })
+  })
+
+  const payload = Buffer.allocUnsafe(2 ** 16).fill('Hello')
+
+  const ws = new WebSocket(`ws://localhost:${server.address().port}`)
+
+  ws.addEventListener('open', () => {
+    ws.send(payload)
+  })
+
+  ws.addEventListener('message', async ({ data }) => {
+    t.type(data, Blob)
+    t.equal(data.size, payload.length)
+    t.same(Buffer.from(await data.arrayBuffer()), payload)
+
+    ws.close()
+    server.close()
+  })
+})