--- a/dom/media/webspeech/synth/test/nsFakeSynthServices.cpp
+++ b/dom/media/webspeech/synth/test/nsFakeSynthServices.cpp
@@ -263,18 +263,17 @@ FakeIndirectAudioSynth::Speak(const nsAS
   uint32_t flags = 0;
   for (uint32_t i = 0; i < ArrayLength(sIndirectVoices); i++) {
     if (aUri.EqualsASCII(sIndirectVoices[i].uri)) {
       flags = sIndirectVoices[i].flags;
     }
   }
 
   if (flags & eFailAtStart) {
-    aTask->DispatchError(0, 0);
-    return NS_OK;
+    return NS_ERROR_FAILURE;
   }
 
   RefPtr<FakeSynthCallback> cb = new FakeSynthCallback(
     (flags & eSuppressEvents) ? nullptr : aTask);
 
   aTask->Setup(cb, 0, 0, 0);
 
   nsCOMPtr<nsIRunnable> runnable = new DispatchStart(aTask);