diff --git a/dom/streams/TransformStreamDefaultController.cpp b/dom/streams/TransformStreamDefaultController.cpp
index 055dd4d883e5..4076114d514c 100644
--- a/dom/streams/TransformStreamDefaultController.cpp
+++ b/dom/streams/TransformStreamDefaultController.cpp
@@ -101,7 +101,7 @@ void SetUpTransformStreamDefaultControllerFromTransformer(
     // Step 2. Let transformAlgorithm be the following steps, taking a chunk
     // argument:
     transformAlgorithm = [](JSContext* aCx,
-                            TransformStreamDefaultController aController,
+                            TransformStreamDefaultController& aController,
                             JS::HandleValue aChunk,
                             ErrorResult& aRv) -> already_AddRefed<Promise> {
       MOZ_ASSERT(!aController.GetTransformCallback());
@@ -127,7 +127,7 @@ void SetUpTransformStreamDefaultControllerFromTransformer(
     controller->SetTransformerMembers(aTransformerDict.mTransform.Value(),
                                       aTransformer);
     transformAlgorithm =
-        [](JSContext* aCx, TransformStreamDefaultController aController,
+        [](JSContext* aCx, TransformStreamDefaultController& aController,
            JS::HandleValue aChunk, ErrorResult& aRv)
             MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION -> already_AddRefed<Promise> {
       MOZ_ASSERT(aController.GetTransformCallback());
diff --git a/dom/streams/TransformStreamDefaultController.h b/dom/streams/TransformStreamDefaultController.h
index 82c956c5efc5..15f5cecf71d7 100644
--- a/dom/streams/TransformStreamDefaultController.h
+++ b/dom/streams/TransformStreamDefaultController.h
@@ -28,7 +28,7 @@ class TransformStreamDefaultController final : public nsISupports,
                                                public nsWrapperCache {
  public:
   using TransformAlgorithm = already_AddRefed<Promise> (*)(
-      JSContext* aCx, TransformStreamDefaultController aController,
+      JSContext* aCx, TransformStreamDefaultController& aController,
       JS::HandleValue aChunk, ErrorResult& aRv);
 
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS