diff --git a/lib/cache/memory-cache-store.js b/lib/cache/memory-cache-store.js
index fd9927ba169..ae6d6614d82 100644
--- a/lib/cache/memory-cache-store.js
+++ b/lib/cache/memory-cache-store.js
@@ -366,7 +366,7 @@ class MemoryStoreWritableStream extends Writable {
     super()
     this.#value = value
     this.#value.readLock = true
-    this.#maxEntrySize = maxEntrySize
+    this.#maxEntrySize = maxEntrySize ?? Infinity
   }
 
   get rawTrailers () {
@@ -374,7 +374,7 @@ class MemoryStoreWritableStream extends Writable {
   }
 
   /**
-   * @param {Buffer[] | undefined} trailers
+   * @param {string[] | undefined} trailers
    */
   set rawTrailers (trailers) {
     this.#value.opts.rawTrailers = trailers
diff --git a/lib/core/constants.js b/lib/core/constants.js
index e450fc6087e..088cf47d80f 100644
--- a/lib/core/constants.js
+++ b/lib/core/constants.js
@@ -112,11 +112,14 @@ Object.setPrototypeOf(headerNameLowerCasedRecord, null)
  */
 const wellknownHeaderNameBuffers = {}
 
+// Note: object prototypes should not be able to be referenced. e.g. `Object#hasOwnProperty`.
+Object.setPrototypeOf(wellknownHeaderNameBuffers, null)
+
 /**
  * @param {string} header Lowercased header
  * @returns {Buffer}
  */
-function getWellknownHeaderNameBuffer (header) {
+function getHeaderNameAsBuffer (header) {
   let buffer = wellknownHeaderNameBuffers[header]
 
   if (buffer === undefined) {
@@ -136,6 +139,5 @@ for (let i = 0; i < wellknownHeaderNames.length; ++i) {
 module.exports = {
   wellknownHeaderNames,
   headerNameLowerCasedRecord,
-  wellknownHeaderNameBuffers,
-  getWellknownHeaderNameBuffer
+  getHeaderNameAsBuffer
 }
diff --git a/lib/core/util.js b/lib/core/util.js
index 07a198f1fab..c37f213349b 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -10,7 +10,7 @@ const nodeUtil = require('node:util')
 const { stringify } = require('node:querystring')
 const { EventEmitter: EE } = require('node:events')
 const { InvalidArgumentError } = require('./errors')
-const { headerNameLowerCasedRecord, getWellknownHeaderNameBuffer } = require('./constants')
+const { headerNameLowerCasedRecord, getHeaderNameAsBuffer } = require('./constants')
 const { tree } = require('./tree')
 
 const [nodeMajor, nodeMinor] = process.versions.node.split('.').map(v => Number(v))
@@ -462,7 +462,7 @@ function encodeHeaders (headers) {
       rawValue = Buffer.from(value)
     }
 
-    const headerBuffer = getWellknownHeaderNameBuffer(header)
+    const headerBuffer = getHeaderNameAsBuffer(header)
 
     rawHeaders[rawHeadersIndex] = headerBuffer
     rawHeadersIndex++
diff --git a/lib/handler/cache-handler.js b/lib/handler/cache-handler.js
index 91b2d65ef5e..ddf8a1171bc 100644
--- a/lib/handler/cache-handler.js
+++ b/lib/handler/cache-handler.js
@@ -59,22 +59,19 @@ class CacheHandler extends DecoratorHandler {
    * @param {Buffer[]} rawHeaders
    * @param {() => void} resume
    * @param {string} statusMessage
-   * @param {Record<string, string | string[]> | undefined} headers
    * @returns {boolean}
    */
   onHeaders (
     statusCode,
     rawHeaders,
     resume,
-    statusMessage,
-    headers = util.parseHeaders(rawHeaders)
+    statusMessage
   ) {
     const downstreamOnHeaders = () => this.#handler.onHeaders(
       statusCode,
       rawHeaders,
       resume,
-      statusMessage,
-      headers
+      statusMessage
     )
 
     if (
@@ -101,6 +98,8 @@ class CacheHandler extends DecoratorHandler {
       return downstreamOnHeaders()
     }
 
+    const headers = util.parseHeaders(rawHeaders)
+
     const cacheControlHeader = headers['cache-control']
     const contentLengthHeader = headers['content-length']
 
diff --git a/lib/handler/cache-revalidation-handler.js b/lib/handler/cache-revalidation-handler.js
index cb335d5bb31..4be61477a51 100644
--- a/lib/handler/cache-revalidation-handler.js
+++ b/lib/handler/cache-revalidation-handler.js
@@ -49,15 +49,13 @@ class CacheRevalidationHandler extends DecoratorHandler {
    * @param {Buffer[]} rawHeaders
    * @param {() => void} resume
    * @param {string} statusMessage
-   * @param {string[] | undefined} headers
    * @returns {boolean}
    */
   onHeaders (
     statusCode,
     rawHeaders,
     resume,
-    statusMessage,
-    headers = undefined
+    statusMessage
   ) {
     // https://www.rfc-editor.org/rfc/rfc9111.html#name-handling-a-validation-respo
     if (statusCode === 304) {
@@ -71,8 +69,7 @@ class CacheRevalidationHandler extends DecoratorHandler {
         statusCode,
         rawHeaders,
         resume,
-        statusMessage,
-        headers
+        statusMessage
       )
     }
   }