diff --git a/Build/lib/cache-filesystem.ts b/Build/lib/cache-filesystem.ts
index 99feb760..1b00c554 100644
--- a/Build/lib/cache-filesystem.ts
+++ b/Build/lib/cache-filesystem.ts
@@ -8,10 +8,12 @@ import { fastStringArrayJoin, identity, mergeHeaders } from './misc';
 import { performance } from 'node:perf_hooks';
 import fs from 'node:fs';
 import { stringHash } from './string-hash';
-import { defaultRequestInit, fetchWithLog, ResponseError } from './fetch-retry';
+import { defaultRequestInit, requestWithLog, UndiciResponseError } from './fetch-retry';
+import type { UndiciResponseData } from './fetch-retry';
 import { Custom304NotModifiedError, CustomAbortError, CustomNoETagFallbackError, fetchAssetsWith304, sleepWithAbort } from './fetch-assets';
 
-import type { Response, RequestInit, HeadersInit } from 'undici';
+import type { HeadersInit } from 'undici';
+import type { IncomingHttpHeaders } from 'undici/types/header';
 
 const enum CacheStatus {
   Hit = 'hit',
@@ -68,6 +70,16 @@ export const TTL = {
   TWO_WEEKS: () => randomInt(10, 14) * ONE_DAY
 };
 
+function ensureETag(headers: IncomingHttpHeaders) {
+  if ('etag' in headers && typeof headers.etag === 'string' && headers.etag.length > 0) {
+    return headers.etag;
+  }
+  if ('ETag' in headers && typeof headers.ETag === 'string' && headers.ETag.length > 0) {
+    return headers.ETag;
+  }
+  return '';
+}
+
 export class Cache<S = string> {
   db: Database;
   /** Time before deletion */
@@ -213,12 +225,12 @@ export class Cache<S = string> {
   async applyWithHttp304<T>(
     url: string,
     extraCacheKey: string,
-    fn: (resp: Response) => Promise<T>,
-    opt: Omit<CacheApplyOption<T, S>, 'incrementTtlWhenHit'>,
-    requestInit?: RequestInit
+    fn: (resp: UndiciResponseData) => Promise<T>,
+    opt: Omit<CacheApplyOption<T, S>, 'incrementTtlWhenHit'>
+    // requestInit?: RequestInit
   ): Promise<T> {
     if (opt.temporaryBypass) {
-      return fn(await fetchWithLog(url, requestInit));
+      return fn(await requestWithLog(url));
     }
 
     const baseKey = url + '$' + extraCacheKey;
@@ -227,19 +239,19 @@ export class Cache<S = string> {
 
     const etag = this.get(etagKey);
 
-    const onMiss = async (resp: Response) => {
+    const onMiss = async (resp: UndiciResponseData) => {
       const serializer = 'serializer' in opt ? opt.serializer : identity as any;
 
       const value = await fn(resp);
 
-      if (resp.headers.has('ETag')) {
-        let serverETag = resp.headers.get('ETag')!;
+      let serverETag = ensureETag(resp.headers);
+      if (serverETag) {
         // FUCK someonewhocares.org
         if (url.includes('someonewhocares.org')) {
           serverETag = serverETag.replace('-gzip', '');
         }
 
-        console.log(picocolors.yellow('[cache] miss'), url, { status: resp.status, cachedETag: etag, serverETag });
+        console.log(picocolors.yellow('[cache] miss'), url, { status: resp.statusCode, cachedETag: etag, serverETag });
 
         this.set(etagKey, serverETag, TTL.ONE_WEEK_STATIC);
         this.set(cachedKey, serializer(value), TTL.ONE_WEEK_STATIC);
@@ -257,28 +269,24 @@ export class Cache<S = string> {
 
     const cached = this.get(cachedKey);
     if (cached == null) {
-      return onMiss(await fetchWithLog(url, requestInit));
+      return onMiss(await requestWithLog(url));
     }
 
-    const resp = await fetchWithLog(
+    const resp = await requestWithLog(
       url,
       {
-        ...(requestInit ?? defaultRequestInit),
         headers: (typeof etag === 'string' && etag.length > 0)
-          ? mergeHeaders(
-            (requestInit ?? defaultRequestInit).headers,
-            { 'If-None-Match': etag }
-          )
-          : (requestInit ?? defaultRequestInit).headers
+          ? { 'If-None-Match': etag }
+          : {}
       }
     );
 
     // Only miss if previously a ETag was present and the server responded with a 304
-    if (resp.headers.has('ETag') && resp.status !== 304) {
+    if (!ensureETag(resp.headers) && resp.statusCode !== 304) {
       return onMiss(resp);
     }
 
-    console.log(picocolors.green(`[cache] ${resp.status === 304 ? 'http 304' : 'cache hit'}`), picocolors.gray(url));
+    console.log(picocolors.green(`[cache] ${resp.statusCode === 304 ? 'http 304' : 'cache hit'}`), picocolors.gray(url));
     this.updateTtl(cachedKey, TTL.ONE_WEEK_STATIC);
 
     const deserializer = 'deserializer' in opt ? opt.deserializer : identity as any;
@@ -297,7 +305,7 @@ export class Cache<S = string> {
     }
 
     if (mirrorUrls.length === 0) {
-      return this.applyWithHttp304(primaryUrl, extraCacheKey, async (resp) => fn(await resp.text()), opt);
+      return this.applyWithHttp304(primaryUrl, extraCacheKey, async (resp) => fn(await resp.body.text()), opt);
     }
 
     const baseKey = primaryUrl + '$' + extraCacheKey;
@@ -323,7 +331,7 @@ export class Cache<S = string> {
       }
 
       const etag = this.get(getETagKey(url));
-      const res = await fetchWithLog(
+      const res = await requestWithLog(
         url,
         {
           signal: controller.signal,
@@ -337,26 +345,26 @@ export class Cache<S = string> {
         }
       );
 
-      const responseHasETag = res.headers.has('etag');
-      if (responseHasETag) {
-        this.set(getETagKey(url), res.headers.get('etag')!, TTL.ONE_WEEK_STATIC);
+      const serverETag = ensureETag(res.headers);
+      if (serverETag) {
+        this.set(getETagKey(url), serverETag, TTL.ONE_WEEK_STATIC);
       }
       // If we do not have a cached value, we ignore 304
-      if (res.status === 304 && typeof previouslyCached === 'string') {
+      if (res.statusCode === 304 && typeof previouslyCached === 'string') {
         controller.abort();
         throw new Custom304NotModifiedError(url, previouslyCached);
       }
-      if (!responseHasETag && !this.get(getETagKey(primaryUrl)) && typeof previouslyCached === 'string') {
+      if (!serverETag && !this.get(getETagKey(primaryUrl)) && typeof previouslyCached === 'string') {
         controller.abort();
         throw new CustomNoETagFallbackError(previouslyCached);
       }
 
       // either no etag and not cached
       // or has etag but not 304
-      const text = await res.text();
+      const text = await res.body.text();
 
       if (text.length < 2) {
-        throw new ResponseError(res);
+        throw new UndiciResponseError(res, url);
       }
 
       controller.abort();
diff --git a/Build/lib/download-publicsuffixlist.ts b/Build/lib/download-publicsuffixlist.ts
index 08cfdeba..8a39fec8 100644
--- a/Build/lib/download-publicsuffixlist.ts
+++ b/Build/lib/download-publicsuffixlist.ts
@@ -4,7 +4,7 @@ import { createMemoizedPromise } from './memo-promise';
 export const getPublicSuffixListTextPromise = createMemoizedPromise(() => fsFetchCache.applyWithHttp304<string[]>(
   'https://publicsuffix.org/list/public_suffix_list.dat',
   getFileContentHash(__filename),
-  (r) => r.text().then(text => text.split('\n')),
+  (r) => r.body.text().then(text => text.split('\n')),
   {
     // https://github.com/publicsuffix/list/blob/master/.github/workflows/tld-update.yml
     // Though the action runs every 24 hours, the IANA list is updated every 7 days.
diff --git a/Build/lib/fetch-assets.ts b/Build/lib/fetch-assets.ts
index 1162e24f..0e9394e4 100644
--- a/Build/lib/fetch-assets.ts
+++ b/Build/lib/fetch-assets.ts
@@ -1,5 +1,5 @@
 import picocolors from 'picocolors';
-import { defaultRequestInit, fetchWithLog, ResponseError } from './fetch-retry';
+import { defaultRequestInit, requestWithLog, UndiciResponseError } from './fetch-retry';
 import { setTimeout } from 'node:timers/promises';
 
 // eslint-disable-next-line sukka/unicorn/custom-error-definition -- typescript is better
@@ -59,11 +59,11 @@ export async function fetchAssetsWith304(url: string, fallbackUrls: string[] | r
       console.log(picocolors.gray('[fetch cancelled]'), picocolors.gray(url));
       throw new CustomAbortError();
     }
-    const res = await fetchWithLog(url, { signal: controller.signal, ...defaultRequestInit });
-    const text = await res.text();
+    const res = await requestWithLog(url, { signal: controller.signal, ...defaultRequestInit });
+    const text = await res.body.text();
 
     if (text.length < 2) {
-      throw new ResponseError(res);
+      throw new UndiciResponseError(res, url);
     }
 
     controller.abort();
diff --git a/Build/lib/fetch-retry.ts b/Build/lib/fetch-retry.ts
index e99a2433..25bf557e 100644
--- a/Build/lib/fetch-retry.ts
+++ b/Build/lib/fetch-retry.ts
@@ -1,12 +1,15 @@
 import picocolors from 'picocolors';
-import {
-  fetch,
+import undici, {
   interceptors,
   EnvHttpProxyAgent,
   setGlobalDispatcher
 } from 'undici';
 
-import type { Response, RequestInit, RequestInfo } from 'undici';
+import type {
+  Dispatcher
+} from 'undici';
+
+export type UndiciResponseData<T = any> = Dispatcher.ResponseData<T>;
 
 import CacheableLookup from 'cacheable-lookup';
 import type { LookupOptions as CacheableLookupOptions } from 'cacheable-lookup';
@@ -111,25 +114,22 @@ function calculateRetryAfterHeader(retryAfter: string) {
   return new Date(retryAfter).getTime() - current;
 }
 
-export class ResponseError extends Error {
-  readonly res: Response;
+export class UndiciResponseError extends Error {
   readonly code: number;
   readonly statusCode: number;
-  readonly url: string;
 
-  constructor(res: Response) {
-    super(res.statusText);
+  constructor(public readonly res: UndiciResponseData, public readonly url: string) {
+    super('HTTP ' + res.statusCode);
 
     if ('captureStackTrace' in Error) {
-      Error.captureStackTrace(this, ResponseError);
+      Error.captureStackTrace(this, UndiciResponseError);
     }
 
     // eslint-disable-next-line sukka/unicorn/custom-error-definition -- deliberatly use previous name
     this.name = this.constructor.name;
     this.res = res;
-    this.code = res.status;
-    this.statusCode = res.status;
-    this.url = res.url;
+    this.code = res.statusCode;
+    this.statusCode = res.statusCode;
   }
 }
 
@@ -139,17 +139,15 @@ export const defaultRequestInit = {
   }
 };
 
-export async function fetchWithLog(url: RequestInfo, opts: RequestInit = defaultRequestInit) {
+export async function requestWithLog(url: string, opt?: Parameters<typeof undici.request>[1]) {
   try {
-    // this will be retried
-    const res = (await fetch(url, opts));
-
-    if (res.status >= 400) {
-      throw new ResponseError(res);
+    const res = await undici.request(url, opt);
+    if (res.statusCode >= 400) {
+      throw new UndiciResponseError(res, url);
     }
 
-    if (!res.ok && res.status !== 304) {
-      throw new ResponseError(res);
+    if (!(res.statusCode >= 200 && res.statusCode <= 299) && res.statusCode !== 304) {
+      throw new UndiciResponseError(res, url);
     }
 
     return res;
@@ -167,4 +165,4 @@ export async function fetchWithLog(url: RequestInfo, opts: RequestInit = default
 
     throw err;
   }
-};
+}
diff --git a/Build/lib/fetch-text-by-line.ts b/Build/lib/fetch-text-by-line.ts
index 604b701d..3524e9d1 100644
--- a/Build/lib/fetch-text-by-line.ts
+++ b/Build/lib/fetch-text-by-line.ts
@@ -8,6 +8,7 @@ import { TextDecoderStream } from 'node:stream/web';
 import { processLine } from './process-line';
 import { $fetch } from './make-fetch-happen';
 import type { NodeFetchResponse } from './make-fetch-happen';
+import type { UndiciResponseData } from './fetch-retry';
 
 function getReadableStream(file: string | FileHandle): ReadableStream {
   if (typeof file === 'string') {
@@ -21,22 +22,26 @@ export const readFileByLine: ((file: string | FileHandle) => AsyncIterable<strin
   .pipeThrough(new TextDecoderStream())
   .pipeThrough(new TextLineStream());
 
-function ensureResponseBody<T extends Response | NodeFetchResponse>(resp: T): NonNullable<T['body']> {
+function ensureResponseBody<T extends Response | NodeFetchResponse | UndiciResponseData>(resp: T): NonNullable<T['body']> {
   if (!resp.body) {
     throw new Error('Failed to fetch remote text');
   }
-  if (resp.bodyUsed) {
+  if ('bodyUsed' in resp && resp.bodyUsed) {
     throw new Error('Body has already been consumed.');
   }
   return resp.body;
 }
 
-export const createReadlineInterfaceFromResponse: ((resp: Response | NodeFetchResponse) => AsyncIterable<string>) = (resp) => {
+export const createReadlineInterfaceFromResponse: ((resp: Response | NodeFetchResponse | UndiciResponseData) => AsyncIterable<string>) = (resp) => {
   const stream = ensureResponseBody(resp);
 
   const webStream: ReadableStream<Uint8Array> = 'getReader' in stream
     ? stream
-    : Readable.toWeb(new Readable().wrap(stream)) as any;
+    : (
+      'body' in stream
+        ? stream.body
+        : Readable.toWeb(new Readable().wrap(stream)) as any
+    );
 
   return webStream
     .pipeThrough(new TextDecoderStream())
diff --git a/Build/lib/parse-dnsmasq.ts b/Build/lib/parse-dnsmasq.ts
index 967c0b11..cbdcd748 100644
--- a/Build/lib/parse-dnsmasq.ts
+++ b/Build/lib/parse-dnsmasq.ts
@@ -2,6 +2,7 @@ import { createReadlineInterfaceFromResponse } from './fetch-text-by-line';
 import { parse as tldtsParse } from 'tldts';
 import { $fetch } from './make-fetch-happen';
 import type { NodeFetchResponse } from './make-fetch-happen';
+import type { UndiciResponseData } from './fetch-retry';
 
 function isDomainLoose(domain: string): boolean {
   const { isIcann, isPrivate, isIp } = tldtsParse(domain);
@@ -15,7 +16,7 @@ export function extractDomainsFromFelixDnsmasq(line: string): string | null {
   return null;
 }
 
-export async function parseFelixDnsmasqFromResp(resp: Response | NodeFetchResponse): Promise<string[]> {
+export async function parseFelixDnsmasqFromResp(resp: NodeFetchResponse | UndiciResponseData): Promise<string[]> {
   const results: string[] = [];
 
   for await (const line of createReadlineInterfaceFromResponse(resp)) {