--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -10584,26 +10584,25 @@ NS_IMPL_CYCLE_COLLECTION(UnblockParsingP
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(UnblockParsingPromiseHandler)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(UnblockParsingPromiseHandler)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(UnblockParsingPromiseHandler)
 
 already_AddRefed<Promise>
-nsIDocument::BlockParsing(OwningNonNull<Promise> aPromise,
-                          ErrorResult& aRv)
-{
-  RefPtr<Promise> resultPromise = Promise::Create(aPromise->GetParentObject(), aRv);
+nsIDocument::BlockParsing(Promise& aPromise, ErrorResult& aRv)
+{
+  RefPtr<Promise> resultPromise = Promise::Create(aPromise.GetParentObject(), aRv);
   if (aRv.Failed()) {
     return nullptr;
   }
 
   RefPtr<PromiseNativeHandler> promiseHandler = new UnblockParsingPromiseHandler(this, resultPromise);
-  aPromise->AppendNativeHandler(promiseHandler);
+  aPromise.AppendNativeHandler(promiseHandler);
 
   return resultPromise.forget();
 }
 
 already_AddRefed<nsIURI>
 nsIDocument::GetMozDocumentURIIfNotForErrorPages()
 {
   if (mFailedChannel) {

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -2782,17 +2782,17 @@ public:
   {
     return mStyleSheetChangeEventsEnabled;
   }
 
   void ObsoleteSheet(nsIURI *aSheetURI, mozilla::ErrorResult& rv);
 
   void ObsoleteSheet(const nsAString& aSheetURI, mozilla::ErrorResult& rv);
 
-  already_AddRefed<mozilla::dom::Promise> BlockParsing(mozilla::OwningNonNull<mozilla::dom::Promise> aPromise,
+  already_AddRefed<mozilla::dom::Promise> BlockParsing(mozilla::dom::Promise& aPromise,
                                                        mozilla::ErrorResult& aRv);
 
   already_AddRefed<nsIURI> GetMozDocumentURIIfNotForErrorPages();
 
   // ParentNode
   nsIHTMLCollection* Children();
   uint32_t ChildElementCount();