--- a/media/webrtc/trunk/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/media/webrtc/trunk/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
@@ -1426,17 +1426,22 @@ uint8_t RTPSender::BuildRIDExtension(
     rtp_header_extension_map_.GetId(kRtpExtensionRtpStreamId,
                                       &id) != 0) {
     // No RtpStreamId or not registered
     return 0;
   }
   size_t pos = 0;
   // RID value is not null-terminated in header, so no +1
   const uint8_t len = strlen(rid_);
-  data_buffer[pos++] = (id << 4) + len;
+  if (len > 16 || len == 0) {
+    LOG(LS_ERROR) << "Failed to add RID header because of unsupported RID"
+                    " length: " << len;
+    return 0;
+  }
+  data_buffer[pos++] = (id << 4) + (len - 1);
   memcpy(data_buffer + pos, rid_, len);
   pos += len;
   return pos;
 }
 
 bool RTPSender::FindHeaderExtensionPosition(RTPExtensionType type,
                                             const uint8_t* rtp_packet,
                                             size_t rtp_packet_length,