diff --git a/tutorial-33/src/main/resources/solidity/AddressBook.sol b/tutorial-33/src/main/resources/solidity/AddressBook.sol
index 4af328b..6f37c18 100644
--- a/tutorial-33/src/main/resources/solidity/AddressBook.sol
+++ b/tutorial-33/src/main/resources/solidity/AddressBook.sol
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 pragma solidity ^0.4.0;
 
 contract AddressBook {