diff --git a/reference-implementation/lib/abstract-ops/miscellaneous.js b/reference-implementation/lib/abstract-ops/miscellaneous.js
index ed55a5268..d4d9a054f 100644
--- a/reference-implementation/lib/abstract-ops/miscellaneous.js
+++ b/reference-implementation/lib/abstract-ops/miscellaneous.js
@@ -24,3 +24,14 @@ exports.CloneAsUint8Array = O => {
 exports.StructuredTransferOrClone = (value, transferList) => {
   return globalThis.structuredClone(value, { transfer: transferList });
 };
+
+exports.RunCloseSteps = value => {
+  if (typeof value.close === 'function') {
+    return;
+  }
+  try {
+    value.close();
+  } catch (closeException) {
+    // Nothing to do.
+  }
+};
diff --git a/reference-implementation/lib/abstract-ops/queue-with-sizes.js b/reference-implementation/lib/abstract-ops/queue-with-sizes.js
index 4cc668e57..2a0d5b21d 100644
--- a/reference-implementation/lib/abstract-ops/queue-with-sizes.js
+++ b/reference-implementation/lib/abstract-ops/queue-with-sizes.js
@@ -1,6 +1,6 @@
 'use strict';
 const assert = require('assert');
-const { IsNonNegativeNumber, StructuredTransferOrClone } = require('./miscellaneous.js');
+const { IsNonNegativeNumber, RunCloseSteps, StructuredTransferOrClone } = require('./miscellaneous.js');
 
 exports.DequeueValue = container => {
   assert('_queue' in container && '_queueTotalSize' in container);
@@ -24,7 +24,7 @@ exports.EnqueueValueWithSize = (container, value, size, transferList) => {
   if (size === Infinity) {
     throw new RangeError('Size must be a finite, non-NaN, non-negative number.');
   }
-  if (container._isOwning) {
+  if (container._isOwning && !container._isPipeToOptimizedTransfer) {
     value = StructuredTransferOrClone(value, transferList);
   }
   container._queue.push({ value, size });
@@ -45,13 +45,7 @@ exports.ResetQueue = container => {
   if (container._isOwning) {
     while (container._queue.length > 0) {
       const value = exports.DequeueValue(container);
-      if (typeof value.close === 'function') {
-        try {
-          value.close();
-        } catch (closeException) {
-          // Nothing to do.
-        }
-      }
+      RunCloseSteps(value);
     }
   }
   container._queue = [];
diff --git a/reference-implementation/lib/abstract-ops/readable-streams.js b/reference-implementation/lib/abstract-ops/readable-streams.js
index 98b0a35fb..b26223943 100644
--- a/reference-implementation/lib/abstract-ops/readable-streams.js
+++ b/reference-implementation/lib/abstract-ops/readable-streams.js
@@ -6,7 +6,8 @@ const { promiseResolvedWith, promiseRejectedWith, newPromise, resolvePromise, re
   require('../helpers/webidl.js');
 const { CanTransferArrayBuffer, CopyDataBlockBytes, CreateArrayFromList, IsDetachedBuffer, TransferArrayBuffer } =
   require('./ecmascript.js');
-const { CloneAsUint8Array, IsNonNegativeNumber, StructuredTransferOrClone } = require('./miscellaneous.js');
+const { CloneAsUint8Array, IsNonNegativeNumber, RunCloseSteps, StructuredTransferOrClone } =
+  require('./miscellaneous.js');
 const { EnqueueValueWithSize, ResetQueue } = require('./queue-with-sizes.js');
 const { AcquireWritableStreamDefaultWriter, IsWritableStreamLocked, WritableStreamAbort,
         WritableStreamDefaultWriterCloseWithErrorPropagation, WritableStreamDefaultWriterRelease,
@@ -136,6 +137,7 @@ function ReadableStreamPipeTo(source, dest, preventClose, preventAbort, preventC
 
   const reader = AcquireReadableStreamDefaultReader(source);
   const writer = AcquireWritableStreamDefaultWriter(dest);
+  writer._stream._controller._isPipeToOptimizedTransfer = source._controller._isOwning && dest._controller._isOwning;
 
   source._disturbed = true;
 
@@ -206,7 +208,11 @@ function ReadableStreamPipeTo(source, dest, preventClose, preventAbort, preventC
             {
               chunkSteps: chunk => {
                 currentWrite = transformPromiseWith(
-                  WritableStreamDefaultWriterWrite(writer, chunk), undefined, () => {}
+                  WritableStreamDefaultWriterWrite(writer, chunk), undefined, () => {
+                    if (reader._stream._controller._isOwning) {
+                      RunCloseSteps(chunk);
+                    }
+                  }
                 );
                 resolveRead(false);
               },
@@ -319,6 +325,7 @@ function ReadableStreamPipeTo(source, dest, preventClose, preventAbort, preventC
     }
 
     function finalize(isError, error) {
+      writer._stream._controller._isPipeToOptimizedTransfer = undefined;
       WritableStreamDefaultWriterRelease(writer);
       ReadableStreamDefaultReaderRelease(reader);