--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -3347,16 +3347,36 @@ TabParent::DispatchTabChildNotReadyEvent
 
   if (mHasPresented) {
     // We shouldn't dispatch this event because clearly the
     // TabChild _became_ ready by the time we were told to
     // dispatch.
     return;
   }
 
+  if (!mDocShellIsActive) {
+    return;
+  }
+
+  RefPtr<nsFrameLoader> frameLoader = GetFrameLoader(true);
+  if (!frameLoader) {
+    return;
+  }
+
+  nsCOMPtr<Element> frameElement(mFrameElement);
+  nsCOMPtr<nsIFrameLoaderOwner> owner = do_QueryInterface(frameElement);
+  if (!owner) {
+    return;
+  }
+
+  RefPtr<nsFrameLoader> currentFrameLoader = owner->GetFrameLoader();
+  if (currentFrameLoader != frameLoader) {
+    return;
+  }
+
   RefPtr<Event> event = NS_NewDOMEvent(mFrameElement, nullptr, nullptr);
   event->InitEvent(NS_LITERAL_STRING("MozTabChildNotReady"), true, false);
   event->SetTrusted(true);
   event->WidgetEventPtr()->mFlags.mOnlyChromeDispatch = true;
   bool dummy;
   mFrameElement->DispatchEvent(event, &dummy);
 }