diff --git a/webrtc/api/rtcstats_integrationtest.cc b/webrtc/api/rtcstats_integrationtest.cc
index 923997cb45..0f60377eb2 100644
--- a/webrtc/api/rtcstats_integrationtest.cc
+++ b/webrtc/api/rtcstats_integrationtest.cc
@@ -497,7 +497,8 @@ class RTCStatsReportVerifier {
     verifier.TestMemberIsDefined(outbound_stream.packets_sent);
     verifier.TestMemberIsDefined(outbound_stream.bytes_sent);
     verifier.TestMemberIsUndefined(outbound_stream.target_bitrate);
-    verifier.TestMemberIsDefined(outbound_stream.round_trip_time);
+    // TODO(hbos): Defined in video but not audio case. Why? crbug.com/669877
+    verifier.MarkMemberTested(outbound_stream.round_trip_time, true);
     return verifier.ExpectAllMembersSuccessfullyTested();
   }
 
diff --git a/webrtc/api/rtcstatscollector.cc b/webrtc/api/rtcstatscollector.cc
index 5289c4820b..f5d3e5f8b8 100644
--- a/webrtc/api/rtcstatscollector.cc
+++ b/webrtc/api/rtcstatscollector.cc
@@ -197,8 +197,10 @@ void SetOutboundRTPStreamStatsFromMediaSenderInfo(
       static_cast<uint32_t>(media_sender_info.packets_sent);
   outbound_stats->bytes_sent =
       static_cast<uint64_t>(media_sender_info.bytes_sent);
-  outbound_stats->round_trip_time =
-      static_cast<double>(media_sender_info.rtt_ms) / rtc::kNumMillisecsPerSec;
+  if (media_sender_info.rtt_ms >= 0) {
+    outbound_stats->round_trip_time = static_cast<double>(
+        media_sender_info.rtt_ms) / rtc::kNumMillisecsPerSec;
+  }
 }
 
 void SetOutboundRTPStreamStatsFromVoiceSenderInfo(
diff --git a/webrtc/api/rtcstatscollector_unittest.cc b/webrtc/api/rtcstatscollector_unittest.cc
index 6d0b56fc0f..0e1fef0e70 100644
--- a/webrtc/api/rtcstatscollector_unittest.cc
+++ b/webrtc/api/rtcstatscollector_unittest.cc
@@ -1628,6 +1628,102 @@ TEST_F(RTCStatsCollectorTest, CollectRTCOutboundRTPStreamStats_Video) {
   EXPECT_TRUE(report->Get(*expected_video.codec_id));
 }
 
+TEST_F(RTCStatsCollectorTest, CollectRTCOutboundRTPStreamStats_Default) {
+  MockVoiceMediaChannel* voice_media_channel = new MockVoiceMediaChannel();
+  cricket::VoiceChannel voice_channel(
+      test_->worker_thread(), test_->network_thread(), test_->media_engine(),
+      voice_media_channel, nullptr, "VoiceContentName", kDefaultRtcpEnabled,
+      kDefaultSrtpRequired);
+  MockVideoMediaChannel* video_media_channel = new MockVideoMediaChannel();
+  cricket::VideoChannel video_channel(
+      test_->worker_thread(), test_->network_thread(), video_media_channel,
+      nullptr, "VideoContentName", kDefaultRtcpEnabled, kDefaultSrtpRequired);
+
+  cricket::VoiceMediaInfo voice_media_info;
+  voice_media_info.senders.push_back(cricket::VoiceSenderInfo());
+  voice_media_info.senders[0].local_stats.push_back(cricket::SsrcSenderInfo());
+  voice_media_info.senders[0].local_stats[0].ssrc = 1;
+  voice_media_info.senders[0].packets_sent = 2;
+  voice_media_info.senders[0].bytes_sent = 3;
+  voice_media_info.senders[0].rtt_ms = -1;
+  voice_media_info.senders[0].codec_payload_type = rtc::Optional<int>(42);
+
+  cricket::VideoMediaInfo video_media_info;
+  video_media_info.senders.push_back(cricket::VideoSenderInfo());
+  video_media_info.senders[0].local_stats.push_back(cricket::SsrcSenderInfo());
+  video_media_info.senders[0].local_stats[0].ssrc = 1;
+  video_media_info.senders[0].firs_rcvd = 2;
+  video_media_info.senders[0].plis_rcvd = 3;
+  video_media_info.senders[0].nacks_rcvd = 4;
+  video_media_info.senders[0].packets_sent = 5;
+  video_media_info.senders[0].bytes_sent = 6;
+  video_media_info.senders[0].rtt_ms = -1;
+  video_media_info.senders[0].codec_payload_type = rtc::Optional<int>(42);
+
+  EXPECT_CALL(*voice_media_channel, GetStats(_))
+      .WillOnce(DoAll(SetArgPointee<0>(voice_media_info), Return(true)));
+  EXPECT_CALL(*video_media_channel, GetStats(_))
+      .WillOnce(DoAll(SetArgPointee<0>(video_media_info), Return(true)));
+
+  SessionStats session_stats;
+  session_stats.proxy_to_transport["VoiceContentName"] = "TransportName";
+  session_stats.proxy_to_transport["VideoContentName"] = "TransportName";
+  session_stats.transport_stats["TransportName"].transport_name =
+      "TransportName";
+
+  // Make sure the associated |RTCTransportStats| is created.
+  cricket::TransportChannelStats channel_stats;
+  channel_stats.component = cricket::ICE_CANDIDATE_COMPONENT_RTP;
+  session_stats.transport_stats["TransportName"].channel_stats.push_back(
+      channel_stats);
+
+  EXPECT_CALL(test_->session(), GetTransportStats(_))
+      .WillRepeatedly(DoAll(SetArgPointee<0>(session_stats), Return(true)));
+  EXPECT_CALL(test_->session(), voice_channel())
+      .WillRepeatedly(Return(&voice_channel));
+  EXPECT_CALL(test_->session(), video_channel())
+      .WillRepeatedly(Return(&video_channel));
+
+  rtc::scoped_refptr<const RTCStatsReport> report = GetStatsReport();
+
+  RTCOutboundRTPStreamStats expected_audio(
+      "RTCOutboundRTPAudioStream_1", report->timestamp_us());
+  expected_audio.ssrc = "1";
+  expected_audio.is_remote = false;
+  expected_audio.media_type = "audio";
+  expected_audio.transport_id = "RTCTransport_TransportName_" +
+      rtc::ToString<>(cricket::ICE_CANDIDATE_COMPONENT_RTP);
+  expected_audio.codec_id = "RTCCodec_OutboundAudio_42";
+  expected_audio.packets_sent = 2;
+  expected_audio.bytes_sent = 3;
+  // |expected_audio.round_trip_time| should be undefined.
+
+  ASSERT(report->Get(expected_audio.id()));
+  const RTCOutboundRTPStreamStats& audio = report->Get(
+      expected_audio.id())->cast_to<RTCOutboundRTPStreamStats>();
+  EXPECT_EQ(audio, expected_audio);
+
+  RTCOutboundRTPStreamStats expected_video(
+      "RTCOutboundRTPVideoStream_1", report->timestamp_us());
+  expected_video.ssrc = "1";
+  expected_video.is_remote = false;
+  expected_video.media_type = "video";
+  expected_video.transport_id = "RTCTransport_TransportName_" +
+      rtc::ToString<>(cricket::ICE_CANDIDATE_COMPONENT_RTP);
+  expected_video.codec_id = "RTCCodec_OutboundVideo_42";
+  expected_video.fir_count = 2;
+  expected_video.pli_count = 3;
+  expected_video.nack_count = 4;
+  expected_video.packets_sent = 5;
+  expected_video.bytes_sent = 6;
+  // |expected_video.round_trip_time| should be undefined.
+
+  ASSERT(report->Get(expected_video.id()));
+  const RTCOutboundRTPStreamStats& video = report->Get(
+      expected_video.id())->cast_to<RTCOutboundRTPStreamStats>();
+  EXPECT_EQ(video, expected_video);
+}
+
 TEST_F(RTCStatsCollectorTest, CollectRTCTransportStats) {
   std::unique_ptr<cricket::Candidate> rtp_local_candidate = CreateFakeCandidate(
       "42.42.42.42", 42, "protocol", cricket::LOCAL_PORT_TYPE, 42);