diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.cc b/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.cc
index b0a5e781a3..9b06b2501e 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.cc
@@ -20,6 +20,7 @@
 namespace webrtc {
 namespace rtcp {
 constexpr uint8_t Sdes::kPacketType;
+constexpr size_t Sdes::kMaxNumberOfChunks;
 // Source Description (SDES) (RFC 3550).
 //
 //         0                   1                   2                   3
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h b/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h
index 31366ad359..46382ac1a5 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h
@@ -28,6 +28,7 @@ class Sdes : public RtcpPacket {
     std::string cname;
   };
   static constexpr uint8_t kPacketType = 202;
+  static constexpr size_t kMaxNumberOfChunks = 0x1f;
 
   Sdes();
   ~Sdes() override;
@@ -48,8 +49,6 @@ class Sdes : public RtcpPacket {
               RtcpPacket::PacketReadyCallback* callback) const override;
 
  private:
-  static const size_t kMaxNumberOfChunks = 0x1f;
-
   std::vector<Chunk> chunks_;
   size_t block_length_;
 };
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
index 5f2eb759c9..56d991c80f 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
@@ -327,7 +327,10 @@ int32_t RTCPSender::AddMixedCNAME(uint32_t SSRC, const char* c_name) {
   RTC_DCHECK(c_name);
   RTC_DCHECK_LT(strlen(c_name), RTCP_CNAME_SIZE);
   rtc::CritScope lock(&critical_section_rtcp_sender_);
-  if (csrc_cnames_.size() >= kRtpCsrcSize)
+  // One spot is reserved for ssrc_/cname_.
+  // TODO(danilchap): Add support for more than 30 contributes by sending
+  // several sdes packets.
+  if (csrc_cnames_.size() >= rtcp::Sdes::kMaxNumberOfChunks - 1)
     return -1;
 
   csrc_cnames_[SSRC] = c_name;
@@ -463,8 +466,8 @@ std::unique_ptr<rtcp::RtcpPacket> RTCPSender::BuildSDES(
   rtcp::Sdes* sdes = new rtcp::Sdes();
   sdes->AddCName(ssrc_, cname_);
 
-  for (const auto it : csrc_cnames_)
-    sdes->AddCName(it.first, it.second);
+  for (const auto& it : csrc_cnames_)
+    RTC_CHECK(sdes->AddCName(it.first, it.second));
 
   return std::unique_ptr<rtcp::RtcpPacket>(sdes);
 }
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_sender_unittest.cc b/webrtc/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
index 2eccadee84..c79cbb7483 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_sender_unittest.cc
@@ -387,6 +387,19 @@ TEST_F(RtcpSenderTest, SendSdes) {
   EXPECT_EQ("alice@host", parser()->sdes()->chunks()[0].cname);
 }
 
+TEST_F(RtcpSenderTest, SendSdesWithMaxChunks) {
+  rtcp_sender_->SetRTCPStatus(RtcpMode::kReducedSize);
+  EXPECT_EQ(0, rtcp_sender_->SetCNAME("alice@host"));
+  const char cname[] = "smith@host";
+  for (size_t i = 0; i < 30; ++i) {
+    const uint32_t csrc = 0x1234 + i;
+    EXPECT_EQ(0, rtcp_sender_->AddMixedCNAME(csrc, cname));
+  }
+  EXPECT_EQ(0, rtcp_sender_->SendRTCP(feedback_state(), kRtcpSdes));
+  EXPECT_EQ(1, parser()->sdes()->num_packets());
+  EXPECT_EQ(31U, parser()->sdes()->chunks().size());
+}
+
 TEST_F(RtcpSenderTest, SdesIncludedInCompoundPacket) {
   rtcp_sender_->SetRTCPStatus(RtcpMode::kCompound);
   EXPECT_EQ(0, rtcp_sender_->SetCNAME("alice@host"));