diff --git a/src/Multicall2.sol b/src/Multicall2.sol
index a162677..267f604 100644
--- a/src/Multicall2.sol
+++ b/src/Multicall2.sol
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 pragma solidity >=0.5.0;
 pragma experimental ABIEncoderV2;