diff --git a/contracts/interfaces/IW3CVerifiableCredential.sol b/contracts/interfaces/IW3CVerifiableCredential.sol
index 1be66a19..9abfb32e 100644
--- a/contracts/interfaces/IW3CVerifiableCredential.sol
+++ b/contracts/interfaces/IW3CVerifiableCredential.sol
@@ -44,7 +44,7 @@ interface IW3CVerifiableCredential {
     }
 
     struct Credential {
-        uint256 id;
+        string id;
         string[] context;
         string[] _type;
         uint64 expirationDate;