diff --git a/dom/media/AudioStream.cpp b/dom/media/AudioStream.cpp
index 8aa2cc0e5bfd..6a39d3d33556 100644
--- a/dom/media/AudioStream.cpp
+++ b/dom/media/AudioStream.cpp
@@ -148,7 +148,9 @@ AudioStream::AudioStream(DataSource& aSource, uint32_t aInRate,
       mSandboxed(CubebUtils::SandboxEnabled()),
       mPlaybackComplete(false),
       mPlaybackRate(1.0f),
-      mPreservesPitch(true) {}
+      mPreservesPitch(true),
+      mCallbacksStarted(false)
+    {}
 
 AudioStream::~AudioStream() {
   LOG("deleted, state %d", mState.load());
@@ -231,8 +233,8 @@ nsresult AudioStream::Init(AudioDeviceInfo* aSinkInfo)
   auto startTime = TimeStamp::Now();
   TRACE("AudioStream::Init");
 
-  LOG("%s channels: %d, rate: %d", __FUNCTION__, mOutChannels,
-      mAudioClock.GetInputRate());
+  LOG("%s channels: %d, rate: %d", __FUNCTION__, mOutChannels, mAudioClock.GetInputRate());
+
   mSinkInfo = aSinkInfo;
 
   cubeb_stream_params params;
@@ -595,6 +597,9 @@ long AudioStream::DataCallback(void* aBuffer, long aFrames) {
     CubebUtils::GetAudioThreadRegistry()->Register(mAudioThreadId);
   }
   WebCore::DenormalDisabler disabler;
+  if (!mCallbacksStarted) {
+    mCallbacksStarted = true;
+  }
 
   TRACE_AUDIO_CALLBACK_BUDGET(aFrames, mAudioClock.GetInputRate());
   TRACE("AudioStream::DataCallback");
diff --git a/dom/media/AudioStream.h b/dom/media/AudioStream.h
index 04ed62493dcc..86975c6a7124 100644
--- a/dom/media/AudioStream.h
+++ b/dom/media/AudioStream.h
@@ -297,6 +297,9 @@ class AudioStream final {
 
   bool IsPlaybackCompleted() const;
 
+  // Returns true if at least one DataCallback has been called.
+  bool CallbackStarted() const { return mCallbacksStarted; }
+
  protected:
   friend class AudioClock;
 
@@ -386,6 +389,7 @@ class AudioStream final {
   std::atomic<bool> mPreservesPitch;
   // Audio thread only
   bool mAudioThreadChanged = false;
+  Atomic<bool> mCallbacksStarted;
 };
 
 }  // namespace mozilla
diff --git a/dom/media/mediasink/AudioSink.h b/dom/media/mediasink/AudioSink.h
index 74cc793da14d..2877d7aed322 100644
--- a/dom/media/mediasink/AudioSink.h
+++ b/dom/media/mediasink/AudioSink.h
@@ -77,6 +77,12 @@ class AudioSink : private AudioStream::DataSource {
 
   const RefPtr<AudioDeviceInfo>& AudioDevice() { return mAudioDevice; }
 
+  // This returns true if the audio callbacks are being called, and so the
+  // audio stream-based clock is moving forward.
+  bool AudioStreamCallbackStarted() {
+    return mAudioStream && mAudioStream->CallbackStarted();
+  }
+
  private:
   // Allocate and initialize mAudioStream. Returns NS_OK on success.
   nsresult InitializeAudioStream(const PlaybackParams& aParams);
diff --git a/dom/media/mediasink/AudioSinkWrapper.cpp b/dom/media/mediasink/AudioSinkWrapper.cpp
index 21ec7d3b4eed..24eeb9f06376 100644
--- a/dom/media/mediasink/AudioSinkWrapper.cpp
+++ b/dom/media/mediasink/AudioSinkWrapper.cpp
@@ -77,8 +77,7 @@ TimeUnit AudioSinkWrapper::GetPosition(TimeStamp* aTimeStamp) {
   TimeUnit pos;
   TimeStamp t = TimeStamp::Now();
 
-  if (!mAudioEnded && !IsMuted()) {
-    MOZ_ASSERT(mAudioSink);
+  if (!mAudioEnded && !IsMuted() && mAudioSink && mAudioSink->AudioStreamCallbackStarted()) {
     // Rely on the audio sink to report playback position when it is not ended.
     pos = mAudioSink->GetPosition();
     LOGV("%p: Getting position from the Audio Sink %lf", this, pos.ToSeconds());