diff --git a/dom/fetch/Fetch.cpp b/dom/fetch/Fetch.cpp
index d53886e96c..5943d60963 100644
--- a/dom/fetch/Fetch.cpp
+++ b/dom/fetch/Fetch.cpp
@@ -922,10 +922,9 @@ FetchBody<Derived>::BodyUsed() const
   // If this object is disturbed or locked, return false.
   if (mReadableStreamBody) {
     AutoJSAPI jsapi;
-    // If we start tracking ownership, we need something like this.
-    //if (!jsapi.Init(mOwner)) {
-    //  return true;
-    //}
+    if (!jsapi.Init(mOwner)) {
+      return true;
+    }
 
     JSContext* cx = jsapi.cx();
 
diff --git a/dom/fetch/FetchStreamReader.cpp b/dom/fetch/FetchStreamReader.cpp
index 3a24844dd9..702b44a6b6 100644
--- a/dom/fetch/FetchStreamReader.cpp
+++ b/dom/fetch/FetchStreamReader.cpp
@@ -44,7 +44,27 @@ private:
 
 } // anonymous
 
-NS_IMPL_ISUPPORTS(FetchStreamReader, nsIOutputStreamCallback)
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FetchStreamReader)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FetchStreamReader)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(FetchStreamReader)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReader)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FetchStreamReader)
+  NS_INTERFACE_MAP_ENTRY(nsIOutputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIOutputStreamCallback)
+NS_INTERFACE_MAP_END
 
 /* static */ nsresult
 FetchStreamReader::Create(JSContext* aCx, nsIGlobalObject* aGlobal,
diff --git a/dom/fetch/FetchStreamReader.h b/dom/fetch/FetchStreamReader.h
index d71021fdc8..6155ee17ff 100644
--- a/dom/fetch/FetchStreamReader.h
+++ b/dom/fetch/FetchStreamReader.h
@@ -23,7 +23,8 @@ class FetchStreamReader final : public nsIOutputStreamCallback
                               , public PromiseNativeHandler
 {
 public:
-  NS_DECL_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(FetchStreamReader, nsIOutputStreamCallback)
   NS_DECL_NSIOUTPUTSTREAMCALLBACK
 
   // This creates a nsIInputStream able to retrieve data from the ReadableStream
diff --git a/dom/fetch/Response.cpp b/dom/fetch/Response.cpp
index 5055db4e24..3ee5e93d4a 100644
--- a/dom/fetch/Response.cpp
+++ b/dom/fetch/Response.cpp
@@ -36,6 +36,7 @@ NS_IMPL_CYCLE_COLLECTION_CLASS(Response)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Response)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mHeaders)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mFetchStreamReader)
 
   tmp->mReadableStreamBody = nullptr;
   tmp->mReadableStreamReader = nullptr;
@@ -46,6 +47,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Response)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mHeaders)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFetchStreamReader)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Response)