diff --git a/webrtc/modules/audio_coding/neteq/interface/neteq.h b/webrtc/modules/audio_coding/neteq/interface/neteq.h
index 925cb231c4..560e77ba8a 100644
--- a/webrtc/modules/audio_coding/neteq/interface/neteq.h
+++ b/webrtc/modules/audio_coding/neteq/interface/neteq.h
@@ -248,7 +248,7 @@ class NetEq {
 
   // Returns the error code for the last occurred error. If no error has
   // occurred, 0 is returned.
-  virtual int LastError() = 0;
+  virtual int LastError() const = 0;
 
   // Returns the error code last returned by a decoder (audio or comfort noise).
   // When LastError() returns kDecoderErrorCode or kComfortNoiseErrorCode, check
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.cc b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
index edf618efc6..44faa22ad4 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.cc
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
@@ -352,7 +352,7 @@ bool NetEqImpl::GetPlayoutTimestamp(uint32_t* timestamp) {
   return true;
 }
 
-int NetEqImpl::LastError() {
+int NetEqImpl::LastError() const {
   CriticalSectionScoped lock(crit_sect_.get());
   return error_code_;
 }
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.h b/webrtc/modules/audio_coding/neteq/neteq_impl.h
index fc2284d981..348f483c94 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.h
@@ -178,7 +178,7 @@ class NetEqImpl : public webrtc::NetEq {
 
   // Returns the error code for the last occurred error. If no error has
   // occurred, 0 is returned.
-  virtual int LastError() OVERRIDE;
+  virtual int LastError() const OVERRIDE;
 
   // Returns the error code last returned by a decoder (audio or comfort noise).
   // When LastError() returns kDecoderErrorCode or kComfortNoiseErrorCode, check
diff --git a/webrtc/modules/audio_coding/neteq/tools/neteq_rtpplay.cc b/webrtc/modules/audio_coding/neteq/tools/neteq_rtpplay.cc
index 1015e177b5..ef2c0b6b55 100644
--- a/webrtc/modules/audio_coding/neteq/tools/neteq_rtpplay.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/neteq_rtpplay.cc
@@ -289,8 +289,24 @@ int main(int argc, char* argv[]) {
                               static_cast<int>(payload_len),
                               packet->time_ms() * sample_rate_hz / 1000);
       if (error != NetEq::kOK) {
-        std::cerr << "InsertPacket returned error code " << neteq->LastError()
-                  << std::endl;
+        if (neteq->LastError() == NetEq::kUnknownRtpPayloadType) {
+          std::cerr << "RTP Payload type "
+                    << static_cast<int>(rtp_header.header.payloadType)
+                    << " is unknown." << std::endl;
+          std::cerr << "Use --codec_map to view default mapping." << std::endl;
+          std::cerr << "Use --helpshort for information on how to make custom "
+                       "mappings." << std::endl;
+        } else {
+          std::cerr << "InsertPacket returned error code " << neteq->LastError()
+                    << std::endl;
+          std::cerr << "Header data:" << std::endl;
+          std::cerr << "  PT = "
+                    << static_cast<int>(rtp_header.header.payloadType)
+                    << std::endl;
+          std::cerr << "  SN = " << rtp_header.header.sequenceNumber
+                    << std::endl;
+          std::cerr << "  TS = " << rtp_header.header.timestamp << std::endl;
+        }
       }
 
       // Get next packet from file.