--- a/dom/worklet/Worklet.cpp
+++ b/dom/worklet/Worklet.cpp
@@ -25,41 +25,42 @@
 
 namespace mozilla {
 namespace dom {
 
 class ExecutionRunnable final : public Runnable
 {
 public:
   ExecutionRunnable(WorkletFetchHandler* aHandler, Worklet::WorkletType aType,
-                    char16_t* aScriptBuffer, size_t aScriptLength,
+                    JS::UniqueTwoByteChars aScriptBuffer, size_t aScriptLength,
                     const WorkletLoadInfo& aWorkletLoadInfo)
     : Runnable("Worklet::ExecutionRunnable")
     , mHandler(aHandler)
+    , mScriptBuffer(Move(aScriptBuffer))
+    , mScriptLength(aScriptLength)
     , mWorkletType(aType)
-    , mBuffer(aScriptBuffer, aScriptLength,
-              JS::SourceBufferHolder::GiveOwnership)
     , mResult(NS_ERROR_FAILURE)
   {
     MOZ_ASSERT(NS_IsMainThread());
   }
 
   NS_IMETHOD
   Run() override;
 
 private:
   void
   RunOnWorkletThread();
 
   void
   RunOnMainThread();
 
   RefPtr<WorkletFetchHandler> mHandler;
+  JS::UniqueTwoByteChars mScriptBuffer;
+  size_t mScriptLength;
   Worklet::WorkletType mWorkletType;
-  JS::SourceBufferHolder mBuffer;
   nsresult mResult;
 };
 
 // ---------------------------------------------------------------------------
 // WorkletFetchHandler
 
 class WorkletFetchHandler final : public PromiseNativeHandler
                                 , public nsIStreamLoaderObserver
@@ -205,30 +206,30 @@ public:
   {
     MOZ_ASSERT(NS_IsMainThread());
 
     if (NS_FAILED(aStatus)) {
       RejectPromises(aStatus);
       return NS_OK;
     }
 
-    char16_t* scriptTextBuf;
+    JS::UniqueTwoByteChars scriptTextBuf;
     size_t scriptTextLength;
     nsresult rv =
       ScriptLoader::ConvertToUTF16(nullptr, aString, aStringLen,
                                    NS_LITERAL_STRING("UTF-8"), nullptr,
                                    scriptTextBuf, scriptTextLength);
     if (NS_WARN_IF(NS_FAILED(rv))) {
       RejectPromises(rv);
       return NS_OK;
     }
 
     // Moving the ownership of the buffer
     nsCOMPtr<nsIRunnable> runnable =
-      new ExecutionRunnable(this, mWorklet->Type(), scriptTextBuf,
+      new ExecutionRunnable(this, mWorklet->Type(), Move(scriptTextBuf),
                             scriptTextLength, mWorklet->LoadInfo());
 
     RefPtr<WorkletThread> thread = mWorklet->GetOrCreateThread();
     if (!thread) {
       RejectPromises(NS_ERROR_FAILURE);
       return NS_OK;
     }
 
@@ -395,18 +396,20 @@ ExecutionRunnable::RunOnWorkletThread()
   JS::CompileOptions compileOptions(cx);
   compileOptions.setIntroductionType("Worklet");
   compileOptions.setFileAndLine(url.get(), 0);
   compileOptions.setIsRunOnce(true);
   compileOptions.setNoScriptRval(true);
 
   JSAutoCompartment comp(cx, globalObj);
 
+  JS::SourceBufferHolder buffer(mScriptBuffer.release(), mScriptLength,
+                                JS::SourceBufferHolder::GiveOwnership);
   JS::Rooted<JS::Value> unused(cx);
-  if (!JS::Evaluate(cx, compileOptions, mBuffer, &unused)) {
+  if (!JS::Evaluate(cx, compileOptions, buffer, &unused)) {
     ErrorResult error;
     error.MightThrowJSException();
     error.StealExceptionFromJSContext(cx);
     mResult = error.StealNSResult();
     return;
   }
 
   // All done.