diff --git a/envoy/data/accesslog/v2/accesslog.proto b/envoy/data/accesslog/v2/accesslog.proto
index f8058ded..7f58ecac 100644
--- a/envoy/data/accesslog/v2/accesslog.proto
+++ b/envoy/data/accesslog/v2/accesslog.proto
@@ -255,6 +255,9 @@ message TLSProperties {
 
   // Properties of the peer certificate used to negotiate TLS.
   CertificateProperties peer_certificate_properties = 5;
+
+  // The TLS session ID.
+  string tls_session_id = 6;
 }
 
 message HTTPRequestProperties {