onUtteranceCompleted does not get called?

Even though I am setting it correctly:

HashMap<String, String> myHashRender = new HashMap<String, String>();
myHashRender.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, "utid");
mTts.speak("Speak something", TextToSpeech.QUEUE_ADD, myHashRender);

also

mTts.setOnUtteranceCompletedListener(this);

in the onInit function return success. Still the onUtteranceCompleted does not get called. Though there are duplicate questions, but no where I could find the answer.

My Activity also implements OnUtteranceCompletedListener.

Please help.