diff --git a/sdk/android/api/org/webrtc/PeerConnection.java b/sdk/android/api/org/webrtc/PeerConnection.java
index 468413ba2f..56d584e75a 100644
--- a/sdk/android/api/org/webrtc/PeerConnection.java
+++ b/sdk/android/api/org/webrtc/PeerConnection.java
@@ -432,9 +432,10 @@ public class PeerConnection {
   /**
    * Java version of webrtc::SdpSemantics.
    *
-   * Configure the SDP semantics used by this PeerConnection. Note that the
-   * WebRTC 1.0 specification requires UNIFIED_PLAN semantics. The
-   * RtpTransceiver API is only available with UNIFIED_PLAN semantics.
+   * Configure the SDP semantics used by this PeerConnection. That the WebRTC
+   * 1.0 specification requires UNIFIED_PLAN semantics and the RtpTransceiver
+   * API is only available with UNIFIED_PLAN semantics. PLAN_B is being
+   * deprecated and will be removed at a future date.
    *
    * <p>PLAN_B will cause PeerConnection to create offers and answers with at
    * most one audio and one video m= section with multiple RtpSenders and
@@ -448,13 +449,27 @@ public class PeerConnection {
    * will also cause PeerConnection to ignore all but the first a=ssrc lines
    * that form a Plan B stream.
    *
-   * <p>For users who wish to send multiple audio/video streams and need to stay
-   * interoperable with legacy WebRTC implementations, specify PLAN_B.
+   * <p>For users who have to interwork with legacy WebRTC implementations, it
+   * is possible to specify PLAN_B until the code is finally removed
+   * (https://crbug.com/webrtc/13528).
    *
-   * <p>For users who wish to send multiple audio/video streams and/or wish to
-   * use the new RtpTransceiver API, specify UNIFIED_PLAN.
+   * <p>The default SdpSemantics value is about to change to UNIFIED_PLAN.
+   * During a short transition period, NOT_SPECIFIED is used to ensure clients
+   * that don't set SdpSemantics are aware of the change by CHECK-crashing.
+   * TODO(https://crbug.com/webrtc/11121): When the default has changed to
+   * UNIFIED_PLAN, delete NOT_SPECIFIED.
    */
-  public enum SdpSemantics { PLAN_B, UNIFIED_PLAN }
+  public enum SdpSemantics {
+    // TODO(https://crbug.com/webrtc/13528): Remove support for PLAN_B.
+    @Deprecated PLAN_B,
+    UNIFIED_PLAN,
+    // The default SdpSemantics value is about to change to UNIFIED_PLAN. During
+    // a short transition period, NOT_SPECIFIED is used to ensure clients that
+    // don't set SdpSemantics are aware of the change by CHECK-crashing.
+    // TODO(https://crbug.com/webrtc/11121): When the default has changed to
+    // kUnifiedPlan, delete kNotSpecified.
+    NOT_SPECIFIED
+  }
 
   /** Java version of PeerConnectionInterface.RTCConfiguration */
   // TODO(qingsi): Resolve the naming inconsistency of fields with/without units.
@@ -611,7 +626,7 @@ public class PeerConnection {
       screencastMinBitrate = null;
       combinedAudioVideoBwe = null;
       networkPreference = AdapterType.UNKNOWN;
-      sdpSemantics = SdpSemantics.PLAN_B;
+      sdpSemantics = SdpSemantics.NOT_SPECIFIED;
       activeResetSrtpParams = false;
       cryptoOptions = null;
       turnLoggingId = null;
diff --git a/sdk/android/api/org/webrtc/PeerConnectionFactory.java b/sdk/android/api/org/webrtc/PeerConnectionFactory.java
index 2b33c6ccd9..e9cf6d3e21 100644
--- a/sdk/android/api/org/webrtc/PeerConnectionFactory.java
+++ b/sdk/android/api/org/webrtc/PeerConnectionFactory.java
@@ -404,6 +404,7 @@ public class PeerConnectionFactory {
   public PeerConnection createPeerConnection(List<PeerConnection.IceServer> iceServers,
       MediaConstraints constraints, PeerConnection.Observer observer) {
     PeerConnection.RTCConfiguration rtcConfig = new PeerConnection.RTCConfiguration(iceServers);
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
     return createPeerConnection(rtcConfig, constraints, observer);
   }
 
@@ -411,6 +412,7 @@ public class PeerConnectionFactory {
   public PeerConnection createPeerConnection(
       List<PeerConnection.IceServer> iceServers, PeerConnection.Observer observer) {
     PeerConnection.RTCConfiguration rtcConfig = new PeerConnection.RTCConfiguration(iceServers);
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
     return createPeerConnection(rtcConfig, observer);
   }
 
diff --git a/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionEndToEndTest.java b/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionEndToEndTest.java
index d9799ab448..588e64700b 100644
--- a/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionEndToEndTest.java
+++ b/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionEndToEndTest.java
@@ -27,6 +27,7 @@ import java.nio.charset.Charset;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.IdentityHashMap;
 import java.util.List;
@@ -642,6 +643,12 @@ public class PeerConnectionEndToEndTest {
   private static WeakReference<MediaStream> addTracksToPC(PeerConnectionFactory factory,
       PeerConnection pc, VideoSource videoSource, String streamLabel, String videoTrackId,
       String audioTrackId, VideoSink videoSink) {
+    return addTracksToPC(factory, pc, videoSource, streamLabel, videoTrackId, audioTrackId,
+        videoSink, /*useAddStream=*/false);
+  }
+  private static WeakReference<MediaStream> addTracksToPC(PeerConnectionFactory factory,
+      PeerConnection pc, VideoSource videoSource, String streamLabel, String videoTrackId,
+      String audioTrackId, VideoSink videoSink, boolean useAddStream) {
     MediaStream lMS = factory.createLocalMediaStream(streamLabel);
     VideoTrack videoTrack = factory.createVideoTrack(videoTrackId, videoSource);
     assertNotNull(videoTrack);
@@ -653,7 +660,20 @@ public class PeerConnectionEndToEndTest {
     lMS.addTrack(videoTrack);
     lMS.addTrack(
         factory.createAudioTrack(audioTrackId, factory.createAudioSource(new MediaConstraints())));
-    pc.addStream(lMS);
+    if (!useAddStream) {
+      // In Unified Plan, addTrack() is the preferred way of adding tracks.
+      for (AudioTrack track : lMS.audioTracks) {
+        pc.addTrack(track, Collections.singletonList(lMS.getId()));
+      }
+      for (VideoTrack track : lMS.videoTracks) {
+        pc.addTrack(track, Collections.singletonList(lMS.getId()));
+      }
+    } else {
+      // Only in Plan B is addStream() supported. Used by a legacy test not yet
+      // updated to Unified Plan.
+      // TODO(https://crbug.com/webrtc/13528): Remove use of addStream().
+      pc.addStream(lMS);
+    }
     return new WeakReference<MediaStream>(lMS);
   }
 
@@ -680,6 +700,7 @@ public class PeerConnectionEndToEndTest {
                        .createIceServer());
 
     PeerConnection.RTCConfiguration rtcConfig = new PeerConnection.RTCConfiguration(iceServers);
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     ObserverExpectations offeringExpectations = new ObserverExpectations("PCTest:offerer");
     PeerConnection offeringPC = factory.createPeerConnection(rtcConfig, offeringExpectations);
@@ -946,6 +967,7 @@ public class PeerConnectionEndToEndTest {
                        .createIceServer());
 
     PeerConnection.RTCConfiguration rtcConfig = new PeerConnection.RTCConfiguration(iceServers);
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     ObserverExpectations offeringExpectations = new ObserverExpectations("PCTest:offerer");
     PeerConnection offeringPC = factory.createPeerConnection(rtcConfig, offeringExpectations);
@@ -1107,7 +1129,8 @@ public class PeerConnectionEndToEndTest {
         PeerConnectionFactory.builder().setOptions(options).createPeerConnectionFactory();
 
     PeerConnection.RTCConfiguration rtcConfig =
-        new PeerConnection.RTCConfiguration(Arrays.asList());
+        new PeerConnection.RTCConfiguration(Collections.emptyList());
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
     // NONE would prevent any candidate being signaled to the PC.
     rtcConfig.iceTransportsType = PeerConnection.IceTransportsType.NONE;
     // We must have the continual gathering enabled to allow the surfacing of candidates on the ICE
@@ -1173,6 +1196,8 @@ public class PeerConnectionEndToEndTest {
         PeerConnection.IceServer.builder("stun:stun.l.google.com:19302").createIceServer());
 
     PeerConnection.RTCConfiguration rtcConfig = new PeerConnection.RTCConfiguration(iceServers);
+    // TODO(https://crbug.com/webrtc/13528): Update test not to use Plan B.
+    rtcConfig.sdpSemantics = PeerConnection.SdpSemantics.PLAN_B;
 
     ObserverExpectations offeringExpectations = new ObserverExpectations("PCTest:offerer");
     PeerConnection offeringPC = factory.createPeerConnection(rtcConfig, offeringExpectations);
@@ -1198,7 +1223,8 @@ public class PeerConnectionEndToEndTest {
     offeringExpectations.expectRenegotiationNeeded();
     WeakReference<MediaStream> oLMS =
         addTracksToPC(factory, offeringPC, videoSource, "offeredMediaStream", "offeredVideoTrack",
-            "offeredAudioTrack", new ExpectedResolutionSetter(answeringExpectations));
+            "offeredAudioTrack", new ExpectedResolutionSetter(answeringExpectations),
+            /*useAddStream=*/true);
 
     offeringExpectations.expectAddTrack(2);
     answeringExpectations.expectAddTrack(2);
@@ -1232,7 +1258,8 @@ public class PeerConnectionEndToEndTest {
     answeringExpectations.expectRenegotiationNeeded();
     WeakReference<MediaStream> aLMS = addTracksToPC(factory, answeringPC, videoSource,
         "answeredMediaStream", "answeredVideoTrack", "answeredAudioTrack",
-        new ExpectedResolutionSetter(offeringExpectations));
+        new ExpectedResolutionSetter(offeringExpectations),
+        /*useAddStream=*/true);
 
     // Create answer.
     sdpLatch = new SdpObserverLatch();
@@ -1376,8 +1403,10 @@ public class PeerConnectionEndToEndTest {
                                         .setVideoDecoderFactory(new SoftwareVideoDecoderFactory())
                                         .createPeerConnectionFactory();
 
-    // This test is fine with no ICE servers.
-    List<PeerConnection.IceServer> iceServers = new ArrayList<>();
+    // TODO(https://crbug.com/webrtc/13528): Update test not to use Plan B.
+    PeerConnection.RTCConfiguration planBConfig =
+        new PeerConnection.RTCConfiguration(Collections.emptyList());
+    planBConfig.sdpSemantics = PeerConnection.SdpSemantics.PLAN_B;
 
     // Use OfferToReceiveAudio/Video to ensure every offer has an audio and
     // video m= section. Simplifies the test because it means we don't have to
@@ -1391,11 +1420,11 @@ public class PeerConnectionEndToEndTest {
 
     // This PeerConnection will only be used to generate offers.
     ObserverExpectations offeringExpectations = new ObserverExpectations("offerer");
-    PeerConnection offeringPC = factory.createPeerConnection(iceServers, offeringExpectations);
+    PeerConnection offeringPC = factory.createPeerConnection(planBConfig, offeringExpectations);
     assertNotNull(offeringPC);
 
     ObserverExpectations expectations = new ObserverExpectations("PC under test");
-    PeerConnection pcUnderTest = factory.createPeerConnection(iceServers, expectations);
+    PeerConnection pcUnderTest = factory.createPeerConnection(planBConfig, expectations);
     assertNotNull(pcUnderTest);
 
     // Add offerer media stream with just an audio track.
@@ -1403,9 +1432,9 @@ public class PeerConnectionEndToEndTest {
     AudioTrack localAudioTrack =
         factory.createAudioTrack("audio", factory.createAudioSource(new MediaConstraints()));
     localStream.addTrack(localAudioTrack);
-    // TODO(deadbeef): Use addTrack once that's available.
     offeringExpectations.expectRenegotiationNeeded();
-    offeringPC.addStream(localStream);
+    RtpSender audioSender =
+        offeringPC.addTrack(localAudioTrack, Collections.singletonList(localStream.getId()));
     // Create offer.
     SdpObserverLatch sdpLatch = new SdpObserverLatch();
     offeringPC.createOffer(sdpLatch, offerConstraints);
@@ -1435,6 +1464,7 @@ public class PeerConnectionEndToEndTest {
     VideoTrack videoTrack = factory.createVideoTrack("video", videoSource);
     offeringExpectations.expectRenegotiationNeeded();
     localStream.addTrack(videoTrack);
+    offeringPC.addTrack(videoTrack, Collections.singletonList(localStream.getId()));
     // ... and create an updated offer.
     sdpLatch = new SdpObserverLatch();
     offeringPC.createOffer(sdpLatch, offerConstraints);
@@ -1453,6 +1483,7 @@ public class PeerConnectionEndToEndTest {
     offeringExpectations.expectRenegotiationNeeded();
     localStream.removeTrack(localAudioTrack);
     localAudioTrack.dispose();
+    offeringPC.removeTrack(audioSender);
     sdpLatch = new SdpObserverLatch();
     offeringPC.createOffer(sdpLatch, offerConstraints);
     assertTrue(sdpLatch.await());
@@ -1492,7 +1523,8 @@ public class PeerConnectionEndToEndTest {
   @SmallTest
   public void testRollback() throws Exception {
     PeerConnectionFactory factory = PeerConnectionFactory.builder().createPeerConnectionFactory();
-    PeerConnection.RTCConfiguration config = new PeerConnection.RTCConfiguration(Arrays.asList());
+    PeerConnection.RTCConfiguration config =
+        new PeerConnection.RTCConfiguration(Collections.emptyList());
     config.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     ObserverExpectations offeringExpectations = new ObserverExpectations("PCTest:offerer");
diff --git a/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionTest.java b/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionTest.java
index 8478fe5571..7d19143166 100644
--- a/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionTest.java
+++ b/sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionTest.java
@@ -165,6 +165,7 @@ public class PeerConnectionTest {
             .setPassword("fakePassword")
             .createIceServer());
     PeerConnection.RTCConfiguration config = new PeerConnection.RTCConfiguration(iceServers);
+    config.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     // Test configuration options.
     config.continualGatheringPolicy = PeerConnection.ContinualGatheringPolicy.GATHER_CONTINUALLY;
@@ -179,6 +180,7 @@ public class PeerConnectionTest {
   public void testCreationWithCertificate() throws Exception {
     PeerConnectionFactory factory = PeerConnectionFactory.builder().createPeerConnectionFactory();
     PeerConnection.RTCConfiguration config = new PeerConnection.RTCConfiguration(Arrays.asList());
+    config.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     // Test certificate.
     RtcCertificatePem originalCert = RtcCertificatePem.generateCertificate();
@@ -197,6 +199,7 @@ public class PeerConnectionTest {
   public void testCreationWithCryptoOptions() throws Exception {
     PeerConnectionFactory factory = PeerConnectionFactory.builder().createPeerConnectionFactory();
     PeerConnection.RTCConfiguration config = new PeerConnection.RTCConfiguration(Arrays.asList());
+    config.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
 
     assertNull(config.cryptoOptions);
 
diff --git a/sdk/android/src/jni/pc/peer_connection.cc b/sdk/android/src/jni/pc/peer_connection.cc
index ee3c35cb3a..6bcaef4552 100644
--- a/sdk/android/src/jni/pc/peer_connection.cc
+++ b/sdk/android/src/jni/pc/peer_connection.cc
@@ -118,6 +118,9 @@ SdpSemantics JavaToNativeSdpSemantics(JNIEnv* jni,
   if (enum_name == "UNIFIED_PLAN")
     return SdpSemantics::kUnifiedPlan;
 
+  if (enum_name == "NOT_SPECIFIED")
+    return SdpSemantics::kNotSpecified;
+
   RTC_DCHECK_NOTREACHED();
   return SdpSemantics::kPlanB_DEPRECATED;
 }