diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.cc b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
index 57fae8cc0d..3fcd3e3c66 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
@@ -143,7 +143,6 @@ AudioMixerImpl::AudioMixerImpl(std::unique_ptr<AudioProcessing> limiter)
       time_stamp_(0),
       limiter_(std::move(limiter)) {
   SetOutputFrequency(kDefaultFrequency);
-  thread_checker_.DetachFromThread();
 }
 
 AudioMixerImpl::~AudioMixerImpl() {}
@@ -189,7 +188,7 @@ void AudioMixerImpl::Mix(int sample_rate,
                          size_t number_of_channels,
                          AudioFrame* audio_frame_for_mixing) {
   RTC_DCHECK(number_of_channels == 1 || number_of_channels == 2);
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
 
   if (OutputFrequency() != sample_rate) {
     SetOutputFrequency(sample_rate);
@@ -229,13 +228,13 @@ void AudioMixerImpl::Mix(int sample_rate,
 }
 
 void AudioMixerImpl::SetOutputFrequency(int frequency) {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   output_frequency_ = frequency;
   sample_size_ = (output_frequency_ * kFrameDurationInMs) / 1000;
 }
 
 int AudioMixerImpl::OutputFrequency() const {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   return output_frequency_;
 }
 
@@ -259,7 +258,7 @@ bool AudioMixerImpl::RemoveSource(Source* audio_source) {
 }
 
 AudioFrameList AudioMixerImpl::GetAudioFromSources() {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   AudioFrameList result;
   std::vector<SourceFrame> audio_source_mixing_data_list;
   std::vector<SourceFrame> ramp_list;
@@ -312,7 +311,7 @@ AudioFrameList AudioMixerImpl::GetAudioFromSources() {
 
 
 bool AudioMixerImpl::LimitMixedAudio(AudioFrame* mixed_audio) const {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   if (!use_limiter_) {
     return true;
   }
@@ -342,7 +341,7 @@ bool AudioMixerImpl::LimitMixedAudio(AudioFrame* mixed_audio) const {
 
 bool AudioMixerImpl::GetAudioSourceMixabilityStatusForTest(
     AudioMixerImpl::Source* audio_source) const {
-  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   rtc::CritScope lock(&crit_);
 
   const auto non_anonymous_iter =
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.h b/webrtc/modules/audio_mixer/audio_mixer_impl.h
index 500bb7862e..e011e8a340 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.h
@@ -17,7 +17,7 @@
 #include "webrtc/api/audio/audio_mixer.h"
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/base/thread_annotations.h"
-#include "webrtc/base/thread_checker.h"
+#include "webrtc/base/race_checker.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
@@ -83,27 +83,27 @@ class AudioMixerImpl : public AudioMixer {
 
   bool LimitMixedAudio(AudioFrame* mixed_audio) const;
 
-
+  // The critical section lock guards audio source insertion and
+  // removal, which can be done from any thread. The race checker
+  // checks that mixing is done sequentially.
   rtc::CriticalSection crit_;
+  rtc::RaceChecker race_checker_;
 
   // The current sample frequency and sample size when mixing.
-  int output_frequency_ ACCESS_ON(&thread_checker_);
-  size_t sample_size_ ACCESS_ON(&thread_checker_);
+  int output_frequency_ GUARDED_BY(race_checker_);
+  size_t sample_size_ GUARDED_BY(race_checker_);
 
   // List of all audio sources. Note all lists are disjunct
   SourceStatusList audio_source_list_ GUARDED_BY(crit_);  // May be mixed.
 
   // Determines if we will use a limiter for clipping protection during
   // mixing.
-  bool use_limiter_ ACCESS_ON(&thread_checker_);
+  bool use_limiter_ GUARDED_BY(race_checker_);
 
-  uint32_t time_stamp_ ACCESS_ON(&thread_checker_);
-
-  // Ensures that Mix is called from the same thread.
-  rtc::ThreadChecker thread_checker_;
+  uint32_t time_stamp_ GUARDED_BY(race_checker_);
 
   // Used for inhibiting saturation in mixing.
-  std::unique_ptr<AudioProcessing> limiter_ ACCESS_ON(&thread_checker_);
+  std::unique_ptr<AudioProcessing> limiter_ GUARDED_BY(race_checker_);
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioMixerImpl);
 };