--- a/dom/media/webspeech/synth/SpeechSynthesis.cpp
+++ b/dom/media/webspeech/synth/SpeechSynthesis.cpp
@@ -306,19 +306,17 @@ SpeechSynthesis::Observe(nsISupports* aS
   nsCOMPtr<nsISupportsPRUint64> wrapper = do_QueryInterface(aSubject);
   NS_ENSURE_TRUE(wrapper, NS_ERROR_FAILURE);
 
   uint64_t innerID;
   nsresult rv = wrapper->GetData(&innerID);
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (innerID == mInnerID) {
-    if (mCurrentTask) {
-      mCurrentTask->Cancel();
-    }
+    Cancel();
 
     nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
     if (obs) {
       obs->RemoveObserver(this, "inner-window-destroyed");
     }
   }
 
   return NS_OK;