diff --git a/lib/web/fetch/headers.js b/lib/web/fetch/headers.js
index a1dab1050a8..2235f125c65 100644
--- a/lib/web/fetch/headers.js
+++ b/lib/web/fetch/headers.js
@@ -602,12 +602,6 @@ webidl.converters.HeadersInit = function (V) {
   if (webidl.util.Type(V) === 'Object') {
     const iterator = Reflect.get(V, Symbol.iterator)
 
-    // A work-around to ensure we send the properly-cased Headers when V is a Headers object.
-    // Read https://github.com/nodejs/undici/pull/3159#issuecomment-2075537226 before touching, please.
-    if (!util.types.isProxy(V) && kHeadersList in V && iterator === Headers.prototype.entries) { // Headers object
-      return V[kHeadersList].entries
-    }
-
     if (typeof iterator === 'function') {
       return webidl.converters['sequence<sequence<ByteString>>'](V, iterator.bind(V))
     }
diff --git a/lib/web/fetch/request.js b/lib/web/fetch/request.js
index 60626f06a92..ca12576b1f0 100644
--- a/lib/web/fetch/request.js
+++ b/lib/web/fetch/request.js
@@ -459,9 +459,8 @@ class Request {
       // 4. If headers is a Headers object, then for each header in its header
       // list, append header’s name/header’s value to this’s headers.
       if (headers instanceof HeadersList) {
-        for (const { 0: key, 1: val } of headers) {
-          // Note: The header names are already in lowercase.
-          headersList.append(key, val, true)
+        for (const [key, val] of headers) {
+          headersList.append(key, val)
         }
         // Note: Copy the `set-cookie` meta-data.
         headersList.cookies = headers.cookies
diff --git a/test/fetch/headers-case.js b/test/fetch/headers-case.js
deleted file mode 100644
index bd9770b755f..00000000000
--- a/test/fetch/headers-case.js
+++ /dev/null
@@ -1,30 +0,0 @@
-'use strict'
-
-const { fetch, Headers } = require('../..')
-const { createServer } = require('node:http')
-const { once } = require('node:events')
-const { test } = require('node:test')
-const { tspl } = require('@matteo.collina/tspl')
-
-test('Headers retain keys case-sensitive', async (t) => {
-  const assert = tspl(t, { plan: 3 })
-
-  const server = createServer((req, res) => {
-    assert.ok(req.rawHeaders.includes('Content-Type'))
-
-    res.end()
-  }).listen(0)
-
-  t.after(() => server.close())
-  await once(server, 'listening')
-
-  for (const headers of [
-    new Headers([['Content-Type', 'text/plain']]),
-    { 'Content-Type': 'text/plain' },
-    [['Content-Type', 'text/plain']]
-  ]) {
-    await fetch(`http://localhost:${server.address().port}`, {
-      headers
-    })
-  }
-})