diff --git a/modules/audio_processing/test/bitexactness_tools.cc b/modules/audio_processing/test/bitexactness_tools.cc
index c49bb5099f..0e9d369452 100644
--- a/modules/audio_processing/test/bitexactness_tools.cc
+++ b/modules/audio_processing/test/bitexactness_tools.cc
@@ -57,6 +57,7 @@ void ReadFloatSamplesFromStereoFile(size_t samples_per_channel,
                                     size_t num_channels,
                                     InputAudioFile* stereo_pcm_file,
                                     rtc::ArrayView<float> data) {
+  RTC_DCHECK_LE(num_channels, 2);
   RTC_DCHECK_EQ(data.size(), samples_per_channel * num_channels);
   std::vector<int16_t> read_samples(samples_per_channel * 2);
   stereo_pcm_file->Read(samples_per_channel * 2, read_samples.data());
diff --git a/modules/audio_processing/test/bitexactness_tools.h b/modules/audio_processing/test/bitexactness_tools.h
index eb5ee081c3..2d3113276d 100644
--- a/modules/audio_processing/test/bitexactness_tools.h
+++ b/modules/audio_processing/test/bitexactness_tools.h
@@ -29,7 +29,7 @@ std::string GetApmRenderTestVectorFileName(int sample_rate_hz);
 // APM bitexactness test.
 std::string GetApmCaptureTestVectorFileName(int sample_rate_hz);
 
-// Extract float samples from a pcm file.
+// Extract float samples of up to two channels from a pcm file.
 void ReadFloatSamplesFromStereoFile(size_t samples_per_channel,
                                     size_t num_channels,
                                     InputAudioFile* stereo_pcm_file,