diff --git a/src/FetchOpaqueInterceptor.ts b/src/FetchOpaqueInterceptor.ts
index 4d34e68f..66647003 100644
--- a/src/FetchOpaqueInterceptor.ts
+++ b/src/FetchOpaqueInterceptor.ts
@@ -13,7 +13,7 @@ export interface FetchOpaque {
   [symbols.kRequestStartTime]: number;
   // eslint-disable-next-line @typescript-eslint/ban-ts-comment
   // @ts-ignore
-  [symbols.kEnableRequestTiming]: number;
+  [symbols.kEnableRequestTiming]: boolean;
 }
 
 // const internalOpaque = {
diff --git a/src/HttpClient.ts b/src/HttpClient.ts
index 0e3dc0ea..e99f3478 100644
--- a/src/HttpClient.ts
+++ b/src/HttpClient.ts
@@ -40,6 +40,7 @@ import { parseJSON, digestAuthHeader, globalId, performanceTime, isReadable, upd
 import symbols from './symbols.js';
 import { initDiagnosticsChannel } from './diagnosticsChannel.js';
 import { HttpClientConnectTimeoutError, HttpClientRequestTimeoutError } from './HttpClientError.js';
+import { FetchOpaque } from './FetchOpaqueInterceptor.js';
 
 type Exists<T> = T extends undefined ? never : T;
 type UndiciRequestOption = Exists<Parameters<typeof undiciRequest>[1]>;
@@ -150,12 +151,16 @@ export const channels = {
 
 export type RequestDiagnosticsMessage = {
   request: RequestMeta;
+  isSentByFetch?: boolean;
+  fetchOpaque?: FetchOpaque;
 };
 
 export type ResponseDiagnosticsMessage = {
   request: RequestMeta;
   response: RawResponseWithMeta;
   error?: Error;
+  isSentByFetch?: boolean;
+  fetchOpaque?: FetchOpaque;
 };
 
 export interface PoolStat {
diff --git a/src/fetch.ts b/src/fetch.ts
index 2fce60e4..09acdecf 100644
--- a/src/fetch.ts
+++ b/src/fetch.ts
@@ -51,10 +51,12 @@ export interface UrllibRequestInit extends RequestInit {
 
 export type FetchDiagnosticsMessage = {
   fetch: FetchMeta;
+  fetchOpaque: FetchOpaque;
 };
 
 export type FetchResponseDiagnosticsMessage = {
   fetch: FetchMeta;
+  fetchOpaque: FetchOpaque;
   timingInfo?: UndiciTimingInfo;
   response?: Response;
   error?: Error;
@@ -202,9 +204,12 @@ export class FetchFactory {
     };
     channels.request.publish({
       request: reqMeta,
+      isSentByFetch: true,
+      fetchOpaque: internalOpaque,
     } as RequestDiagnosticsMessage);
     channels.fetchRequest.publish({
       fetch: fetchMeta,
+      fetchOpaque: internalOpaque,
     } as FetchDiagnosticsMessage);
 
     let res: Response;
@@ -239,11 +244,14 @@ export class FetchFactory {
       channels.fetchResponse.publish({
         fetch: fetchMeta,
         error: e,
+        fetchOpaque: internalOpaque,
       } as FetchResponseDiagnosticsMessage);
       channels.response.publish({
         request: reqMeta,
         response: urllibResponse,
         error: e,
+        isSentByFetch: true,
+        fetchOpaque: internalOpaque,
       } as ResponseDiagnosticsMessage);
       throw e;
     }
@@ -265,10 +273,13 @@ export class FetchFactory {
       fetch: fetchMeta,
       timingInfo: state.timingInfo,
       response: res!,
+      fetchOpaque: internalOpaque,
     } as FetchResponseDiagnosticsMessage);
     channels.response.publish({
       request: reqMeta,
       response: urllibResponse,
+      isSentByFetch: true,
+      fetchOpaque: internalOpaque,
     } as ResponseDiagnosticsMessage);
     return res!;
   }