diff --git a/modules/audio_coding/neteq/neteq_impl_unittest.cc b/modules/audio_coding/neteq/neteq_impl_unittest.cc
index b509cec3b1..15ec1f4191 100644
--- a/modules/audio_coding/neteq/neteq_impl_unittest.cc
+++ b/modules/audio_coding/neteq/neteq_impl_unittest.cc
@@ -698,7 +698,10 @@ TEST_F(NetEqImplTest, FirstPacketUnknown) {
 // internal CNG mode properly.
 TEST_F(NetEqImplTest, CodecInternalCng) {
   UseNoMocks();
-  CreateInstance();
+  // Create a mock decoder object.
+  MockAudioDecoder mock_decoder;
+  CreateInstance(
+      new rtc::RefCountedObject<test::AudioDecoderProxyFactory>(&mock_decoder));
 
   const uint8_t kPayloadType = 17;   // Just an arbitrary number.
   const uint32_t kReceiveTime = 17;  // Value doesn't matter for this test.
@@ -715,8 +718,6 @@ TEST_F(NetEqImplTest, CodecInternalCng) {
   rtp_header.timestamp = 0x12345678;
   rtp_header.ssrc = 0x87654321;
 
-  // Create a mock decoder object.
-  MockAudioDecoder mock_decoder;
   EXPECT_CALL(mock_decoder, Reset()).WillRepeatedly(Return());
   EXPECT_CALL(mock_decoder, SampleRateHz())
       .WillRepeatedly(Return(kSampleRateKhz * 1000));
@@ -760,9 +761,8 @@ TEST_F(NetEqImplTest, CodecInternalCng) {
                       SetArgPointee<4>(AudioDecoder::kSpeech),
                       Return(rtc::checked_cast<int>(kPayloadLengthSamples))));
 
-  EXPECT_EQ(NetEq::kOK, neteq_->RegisterExternalDecoder(
-                            &mock_decoder, NetEqDecoder::kDecoderOpus,
-                            "dummy name", kPayloadType));
+  EXPECT_TRUE(neteq_->RegisterPayloadType(kPayloadType,
+                                          SdpAudioFormat("opus", 48000, 2)));
 
   // Insert one packet (decoder will return speech).
   EXPECT_EQ(NetEq::kOK,
@@ -1151,7 +1151,11 @@ TEST_F(NetEqImplTest, DecodingError) {
 // This test checks the behavior of NetEq when audio decoder fails during CNG.
 TEST_F(NetEqImplTest, DecodingErrorDuringInternalCng) {
   UseNoMocks();
-  CreateInstance();
+
+  // Create a mock decoder object.
+  MockAudioDecoder mock_decoder;
+  CreateInstance(
+      new rtc::RefCountedObject<test::AudioDecoderProxyFactory>(&mock_decoder));
 
   const uint8_t kPayloadType = 17;   // Just an arbitrary number.
   const uint32_t kReceiveTime = 17;  // Value doesn't matter for this test.
@@ -1172,8 +1176,6 @@ TEST_F(NetEqImplTest, DecodingErrorDuringInternalCng) {
   rtp_header.timestamp = 0x12345678;
   rtp_header.ssrc = 0x87654321;
 
-  // Create a mock decoder object.
-  MockAudioDecoder mock_decoder;
   EXPECT_CALL(mock_decoder, Reset()).WillRepeatedly(Return());
   EXPECT_CALL(mock_decoder, SampleRateHz())
       .WillRepeatedly(Return(kSampleRateHz));
@@ -1215,9 +1217,8 @@ TEST_F(NetEqImplTest, DecodingErrorDuringInternalCng) {
                   Return(rtc::checked_cast<int>(kFrameLengthSamples))));
   }
 
-  EXPECT_EQ(NetEq::kOK, neteq_->RegisterExternalDecoder(
-                            &mock_decoder, NetEqDecoder::kDecoderPCM16B,
-                            "dummy name", kPayloadType));
+  EXPECT_TRUE(neteq_->RegisterPayloadType(kPayloadType,
+                                          SdpAudioFormat("l16", 8000, 1)));
 
   // Insert 2 packets. This will make netEq into codec internal CNG mode.
   for (int i = 0; i < 2; ++i) {
diff --git a/test/audio_decoder_proxy_factory.h b/test/audio_decoder_proxy_factory.h
index af08581d17..18988e66f7 100644
--- a/test/audio_decoder_proxy_factory.h
+++ b/test/audio_decoder_proxy_factory.h
@@ -74,8 +74,13 @@ class AudioDecoderProxyFactory : public AudioDecoderFactory {
                        int sample_rate_hz,
                        int16_t* decoded,
                        SpeechType* speech_type) override {
-      RTC_NOTREACHED();
-      return -1;
+      // Needed for tests of NetEqImpl::DecodeCng, which calls the deprecated
+      // Decode method.
+      size_t max_decoded_bytes =
+          decoder_->PacketDuration(encoded, encoded_len) *
+          decoder_->Channels() * sizeof(int16_t);
+      return decoder_->Decode(encoded, encoded_len, sample_rate_hz,
+                              max_decoded_bytes, decoded, speech_type);
     }
 
     AudioDecoder* const decoder_;