--- a/dom/media/webspeech/synth/nsSpeechTask.cpp
+++ b/dom/media/webspeech/synth/nsSpeechTask.cpp
@@ -778,15 +778,15 @@ nsSpeechTask::WindowAudioCaptureChanged(
 }
 
 void
 nsSpeechTask::SetAudioOutputVolume(float aVolume)
 {
   if (mStream && !mStream->IsDestroyed()) {
     mStream->SetAudioOutputVolume(this, aVolume);
   }
-  if (mIndirectAudio) {
+  if (mIndirectAudio && mCallback) {
     mCallback->OnVolumeChanged(aVolume);
   }
 }
 
 } // namespace dom
 } // namespace mozilla