diff --git a/quiche/blind_sign_auth/proto/attestation.proto b/quiche/blind_sign_auth/proto/attestation.proto
index 31e31ea..7ab2f56 100644
--- a/quiche/blind_sign_auth/proto/attestation.proto
+++ b/quiche/blind_sign_auth/proto/attestation.proto
@@ -111,6 +111,9 @@
 
   // Device ID for quota checking.
   string device_id = 3;
+
+  // Nonce returned from the server and added to the content bindings.
+  bytes nonce = 4;
 }
 
 message AttestationData {