diff --git a/talk/media/webrtc/webrtcvideoengine2.cc b/talk/media/webrtc/webrtcvideoengine2.cc
index ba96504a77..e7701a1655 100644
--- a/talk/media/webrtc/webrtcvideoengine2.cc
+++ b/talk/media/webrtc/webrtcvideoengine2.cc
@@ -303,6 +303,12 @@ static void MergeFecConfig(const webrtc::FecConfig& other,
     output->red_rtx_payload_type = other.red_rtx_payload_type;
   }
 }
+
+// Returns true if the given codec is disallowed from doing simulcast.
+bool IsCodecBlacklistedForSimulcast(const std::string& codec_name) {
+  return CodecNamesEq(codec_name, kH264CodecName);
+}
+
 }  // namespace
 
 // Constants defined in talk/media/webrtc/constants.h
@@ -2095,9 +2101,17 @@ WebRtcVideoChannel2::WebRtcVideoSendStream::CreateVideoEncoderConfig(
   clamped_codec.width = width;
   clamped_codec.height = height;
 
-  encoder_config.streams = CreateVideoStreams(
-      clamped_codec, parameters_.options, parameters_.max_bitrate_bps,
-      dimensions.is_screencast ? 1 : parameters_.config.rtp.ssrcs.size());
+  // By default, the stream count for the codec configuration should match the
+  // number of negotiated ssrcs. But if the codec is blacklisted for simulcast
+  // or a screencast, only configure a single stream.
+  size_t stream_count = parameters_.config.rtp.ssrcs.size();
+  if (IsCodecBlacklistedForSimulcast(codec.name) || dimensions.is_screencast) {
+    stream_count = 1;
+  }
+
+  encoder_config.streams =
+      CreateVideoStreams(clamped_codec, parameters_.options,
+                         parameters_.max_bitrate_bps, stream_count);
 
   // Conference mode screencast uses 2 temporal layers split at 100kbit.
   if (parameters_.options.conference_mode.GetWithDefaultIfUnset(false) &&
diff --git a/talk/media/webrtc/webrtcvideoengine2_unittest.cc b/talk/media/webrtc/webrtcvideoengine2_unittest.cc
index 2f873796fe..fd87703eab 100644
--- a/talk/media/webrtc/webrtcvideoengine2_unittest.cc
+++ b/talk/media/webrtc/webrtcvideoengine2_unittest.cc
@@ -644,6 +644,29 @@ TEST_F(WebRtcVideoEngine2Test,
   ASSERT_EQ(0u, encoder_factory.encoders().size());
 }
 
+TEST_F(WebRtcVideoEngine2Test, SimulcastDisabledForH264) {
+  cricket::FakeWebRtcVideoEncoderFactory encoder_factory;
+  encoder_factory.AddSupportedVideoCodecType(webrtc::kVideoCodecH264, "H264");
+  std::vector<cricket::VideoCodec> codecs;
+  codecs.push_back(kH264Codec);
+
+  rtc::scoped_ptr<VideoMediaChannel> channel(
+      SetUpForExternalEncoderFactory(&encoder_factory, codecs));
+
+  const std::vector<uint32> ssrcs = MAKE_VECTOR(kSsrcs3);
+  EXPECT_TRUE(
+      channel->AddSendStream(cricket::CreateSimStreamParams("cname", ssrcs)));
+  // Set the stream to 720p. This should trigger a "real" encoder
+  // initialization.
+  cricket::VideoFormat format(
+      1280, 720, cricket::VideoFormat::FpsToInterval(30), cricket::FOURCC_I420);
+  EXPECT_TRUE(channel->SetSendStreamFormat(ssrcs[0], format));
+  ASSERT_EQ(1u, encoder_factory.encoders().size());
+  FakeWebRtcVideoEncoder* encoder = encoder_factory.encoders()[0];
+  EXPECT_EQ(webrtc::kVideoCodecH264, encoder->GetCodecSettings().codecType);
+  EXPECT_EQ(1u, encoder->GetCodecSettings().numberOfSimulcastStreams);
+}
+
 // Test external codec with be added to the end of the supported codec list.
 TEST_F(WebRtcVideoEngine2Test, ReportSupportedExternalCodecs) {
   cricket::FakeWebRtcVideoEncoderFactory encoder_factory;