2 files changed, 21 insertions, 3 deletions
diff --git a/ext/fetch/22_body.js b/ext/fetch/22_body.js
index 9fe00b144..644b9f76f 100644
--- a/ext/fetch/22_body.js
+++ b/ext/fetch/22_body.js
@@ -33,6 +33,7 @@ import {
   readableStreamCollectIntoUint8Array,
   readableStreamDisturb,
   ReadableStreamPrototype,
+  readableStreamTee,
   readableStreamThrowIfErrored,
 } from "ext:deno_web/06_streams.js";
 const primordials = globalThis.__bootstrap.primordials;
@@ -194,7 +195,7 @@ class InnerBody {
    * @returns {InnerBody}
    */
   clone() {
-    const { 0: out1, 1: out2 } = this.stream.tee();
+    const { 0: out1, 1: out2 } = readableStreamTee(this.stream, true);
     this.streamOrStatic = out1;
     const second = new InnerBody(out2);
     second.source = core.deserialize(core.serialize(this.source));
diff --git a/ext/web/06_streams.js b/ext/web/06_streams.js
index beab2ec12..01f84aa2c 100644
--- a/ext/web/06_streams.js
+++ b/ext/web/06_streams.js
@@ -9,6 +9,7 @@
 const core = globalThis.Deno.core;
 const ops = core.ops;
 import * as webidl from "ext:deno_webidl/00_webidl.js";
+import { structuredClone } from "ext:deno_web/02_structured_clone.js";
 import {
   AbortSignalPrototype,
   add,
@@ -2847,9 +2848,24 @@ function readableStreamDefaultTee(stream, cloneForBranch2) {
         queueMicrotask(() => {
           readAgain = false;
           const value1 = value;
-          const value2 = value;
+          let value2 = value;
 
-          // TODO(lucacasonato): respect clonedForBranch2.
+          if (canceled2 === false && cloneForBranch2 === true) {
+            try {
+              value2 = structuredClone(value2);
+            } catch (cloneError) {
+              readableStreamDefaultControllerError(
+                branch1[_controller],
+                cloneError,
+              );
+              readableStreamDefaultControllerError(
+                branch2[_controller],
+                cloneError,
+              );
+              cancelPromise.resolve(readableStreamCancel(stream, cloneError));
+              return;
+            }
+          }
 
           if (canceled1 === false) {
             readableStreamDefaultControllerEnqueue(
@@ -6464,6 +6480,7 @@ export {
   readableStreamForRidUnrefableRef,
   readableStreamForRidUnrefableUnref,
   ReadableStreamPrototype,
+  readableStreamTee,
   readableStreamThrowIfErrored,
   TransformStream,
   TransformStreamDefaultController,