diff --git a/dom/events/Event.cpp b/dom/events/Event.cpp
index c639ca867911..4caeb7399283 100644
--- a/dom/events/Event.cpp
+++ b/dom/events/Event.cpp
@@ -462,14 +462,16 @@ void Event::PreventDefault(JSContext* aCx, CallerType aCallerType) {
 void Event::PreventDefaultInternal(bool aCalledByDefaultHandler,
                                    nsIPrincipal* aPrincipal) {
   if (mEvent->mFlags.mInPassiveListener) {
-    if (nsPIDOMWindowInner* win = mOwner->GetAsInnerWindow()) {
-      if (Document* doc = win->GetExtantDoc()) {
-        if (!doc->HasWarnedAbout(
-                Document::ePreventDefaultFromPassiveListener)) {
-          AutoTArray<nsString, 1> params;
-          GetType(*params.AppendElement());
-          doc->WarnOnceAbout(Document::ePreventDefaultFromPassiveListener,
-                             false, params);
+    if (mOwner) {
+      if (nsPIDOMWindowInner* win = mOwner->GetAsInnerWindow()) {
+        if (Document* doc = win->GetExtantDoc()) {
+          if (!doc->HasWarnedAbout(
+                  Document::ePreventDefaultFromPassiveListener)) {
+            AutoTArray<nsString, 1> params;
+            GetType(*params.AppendElement());
+            doc->WarnOnceAbout(Document::ePreventDefaultFromPassiveListener,
+                               false, params);
+          }
         }
       }
     }
diff --git a/dom/messagechannel/MessagePort.cpp b/dom/messagechannel/MessagePort.cpp
index 417884c31b60..0f99e93607da 100644
--- a/dom/messagechannel/MessagePort.cpp
+++ b/dom/messagechannel/MessagePort.cpp
@@ -119,8 +119,7 @@ class PostMessageRunnable final : public CancelableRunnable {
     }
 
     // Create the event
-    RefPtr<MessageEvent> event =
-        new MessageEvent(mPort->GetOwnerWindow(), nullptr, nullptr);
+    RefPtr<MessageEvent> event = new MessageEvent(mPort, nullptr, nullptr);
 
     Sequence<OwningNonNull<MessagePort>> ports;
     if (!mData->TakeTransferredPortsAsSequence(ports)) {