diff --git a/proto/identity/api/v1/identity.proto b/proto/identity/api/v1/identity.proto
index ae933a2..2b584e0 100644
--- a/proto/identity/api/v1/identity.proto
+++ b/proto/identity/api/v1/identity.proto
@@ -67,6 +67,7 @@ message UnverifiedSmartContractWalletSignature {
 message VerifySmartContractWalletSignaturesResponse {
   message ValidationResponse {
     bool is_valid = 1;
+    optional string error = 2;
   }
 
   repeated ValidationResponse responses = 1;