diff --git a/dom/webserial/SerialPort.cpp b/dom/webserial/SerialPort.cpp
index 818fb9acea0..d5dcee6705a 100644
--- a/dom/webserial/SerialPort.cpp
+++ b/dom/webserial/SerialPort.cpp
@@ -137,7 +137,7 @@ void SerialPort::Shutdown() {
   if (mState == State::Opened || mState == State::Closing) {
     mState = State::Closed;
     // Don't have to wait for this
-    RefPtr<Promise> ignoredPromise = CloseStreams();
+    RefPtr<Promise> ignoredPromise = CloseStreams(StreamCloseMode::Forced);
   }
 
   if (mOpenPromise) {
@@ -529,7 +529,7 @@ already_AddRefed<Promise> SerialPort::Close(ErrorResult& aRv) {
   // promise to wait for all (steps 5-8). Our pendingClosePromise is
   // effectively resolved once both streams are nulled (step 6), so the
   // combined promise just waits for the cancel and abort to finish.
-  RefPtr<Promise> combinedPromise = CloseStreams();
+  RefPtr<Promise> combinedPromise = CloseStreams(StreamCloseMode::Graceful);
   if (!combinedPromise) {
     combinedPromise = Promise::CreateResolvedWithUndefined(global, aRv);
     if (NS_WARN_IF(aRv.Failed())) {
@@ -598,7 +598,7 @@ already_AddRefed<Promise> SerialPort::Forget(ErrorResult& aRv) {
 
   if (wasActive) {
     // Don't have to wait for this
-    RefPtr<Promise> ignoredPromise = CloseStreams();
+    RefPtr<Promise> ignoredPromise = CloseStreams(StreamCloseMode::Graceful);
   }
 
   UpdateWorkerRef();
@@ -652,7 +652,7 @@ void SerialPort::MarkForgotten() {
 
   if (wasActive) {
     // Don't have to wait for this
-    RefPtr<Promise> ignoredPromise = CloseStreams();
+    RefPtr<Promise> ignoredPromise = CloseStreams(StreamCloseMode::Graceful);
   }
 
   UpdateWorkerRef();
@@ -767,7 +767,7 @@ void SerialPort::NotifyDisconnected() {
   }
   mPhysicallyPresent = false;
   // Don't have to wait for this
-  RefPtr<Promise> ignoredPromise = CloseStreams();
+  RefPtr<Promise> ignoredPromise = CloseStreams(StreamCloseMode::Graceful);
   UpdateWorkerRef();
   NotifySharingStateChanged(false);
 
@@ -951,7 +951,7 @@ void SerialPort::SettleClosePromise(nsresult aResult) {
   }
 }
 
-already_AddRefed<Promise> SerialPort::CloseStreams() {
+already_AddRefed<Promise> SerialPort::CloseStreams(StreamCloseMode aMode) {
   nsIGlobalObject* global = GetRelevantGlobal();
   if (!global) {
     return nullptr;
@@ -963,8 +963,9 @@ already_AddRefed<Promise> SerialPort::CloseStreams() {
 
   MOZ_LOG(gWebSerialLog, LogLevel::Info,
           ("SerialPort[%p]::CloseStreams closing streams "
-           "(readable=%p, writable=%p)",
-           this, mReadable.get(), mWritable.get()));
+           "(readable=%p, writable=%p, mode=%s)",
+           this, mReadable.get(), mWritable.get(),
+           aMode == StreamCloseMode::Forced ? "forced" : "graceful"));
 
   AutoJSAPI jsapi;
   if (!jsapi.Init(global)) {
@@ -973,14 +974,33 @@ already_AddRefed<Promise> SerialPort::CloseStreams() {
 
   JSContext* cx = jsapi.cx();
 
-  // Cancel the readable and abort the writable, collecting their promises.
-  nsTArray<RefPtr<Promise>> streamPromises;
-
   RefPtr<DOMException> exception =
       DOMException::Create(NS_ERROR_DOM_NETWORK_ERR, "Port has been closed"_ns);
   JS::Rooted<JS::Value> errorVal(cx);
   bool hasError = ToJSValue(cx, exception, &errorVal);
 
+  // Error the streams instead of aborting, so we don't dispatchevents
+  // or runauthor-visible algorithms. The OS resources are released by
+  // mChild->Shutdown() in Shutdown().
+  if (aMode == StreamCloseMode::Forced) {
+    if (mReadable && hasError) {
+      IgnoredErrorResult rv;
+      RefPtr readable = mReadable;
+      readable->ErrorNative(cx, errorVal, rv);
+    }
+    if (mWritable && hasError) {
+      IgnoredErrorResult rv;
+      RefPtr writable = mWritable;
+      writable->ErrorNative(cx, errorVal, rv);
+    }
+    mReadable = nullptr;
+    mWritable = nullptr;
+    return nullptr;
+  }
+
+  // Cancel the readable and abort the writable, collecting their promises.
+  nsTArray<RefPtr<Promise>> streamPromises;
+
   if (mReadable && hasError) {
     IgnoredErrorResult rv;
     RefPtr readable = mReadable;
diff --git a/dom/webserial/SerialPort.h b/dom/webserial/SerialPort.h
index fb319115eaa..3950affdafe 100644
--- a/dom/webserial/SerialPort.h
+++ b/dom/webserial/SerialPort.h
@@ -116,11 +116,21 @@ class SerialPort final : public DOMEventTargetHelper {
  private:
   ~SerialPort() override;
 
+  enum class StreamCloseMode : uint8_t {
+    // Cancel the readable and abort the writable, running their underlying
+    // source/sink algorithms.
+    Graceful,
+    // Error both streams without running author-observable algorithms or
+    // dispatching events.
+    Forced,
+  };
+
   MOZ_CAN_RUN_SCRIPT ReadableStream* CreateReadableStream();
   MOZ_CAN_RUN_SCRIPT WritableStream* CreateWritableStream();
   void CloseAfterStreamsClosed();
   void SettleClosePromise(nsresult aResult);
-  MOZ_CAN_RUN_SCRIPT already_AddRefed<Promise> CloseStreams();
+  MOZ_CAN_RUN_SCRIPT already_AddRefed<Promise> CloseStreams(
+      StreamCloseMode aMode);
   void NotifySharingStateChanged(bool aConnected);
   void UpdateWorkerRef();