diff --git a/contracts/SimpleMultiSig.sol b/contracts/SimpleMultiSig.sol
index 34036c5..3848308 100644
--- a/contracts/SimpleMultiSig.sol
+++ b/contracts/SimpleMultiSig.sol
@@ -1,4 +1,5 @@
-pragma solidity ^0.4.24;
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.4;
 
 contract SimpleMultiSig {
 
@@ -25,7 +26,7 @@ bytes32 constant SALT = 0x251543af6a222378665a76fe38dbceae4871a070b7fdaf5c6c30cf
   bytes32 DOMAIN_SEPARATOR;          // hash for EIP712, computed from contract address
   
   // Note that owners_ must be strictly increasing, in order to prevent duplicates
-  constructor(uint threshold_, address[] owners_, uint chainId) public {
+  constructor(uint threshold_, address[] memory owners_, uint chainId) {
     require(owners_.length <= 10 && threshold_ <= owners_.length && threshold_ > 0);
 
     address lastAdd = address(0);
@@ -46,7 +47,7 @@ bytes32 constant SALT = 0x251543af6a222378665a76fe38dbceae4871a070b7fdaf5c6c30cf
   }
 
   // Note that address recovered from signatures must be strictly increasing, in order to prevent duplicates
-  function execute(uint8[] sigV, bytes32[] sigR, bytes32[] sigS, address destination, uint value, bytes data, address executor, uint gasLimit) public {
+  function execute(uint8[] memory sigV, bytes32[] memory sigR, bytes32[] memory sigS, address destination, uint value, bytes memory data, address executor, uint gasLimit) public {
     require(sigR.length == threshold);
     require(sigR.length == sigS.length && sigR.length == sigV.length);
     require(executor == msg.sender || executor == address(0));
@@ -71,5 +72,8 @@ bytes32 constant SALT = 0x251543af6a222378665a76fe38dbceae4871a070b7fdaf5c6c30cf
     require(success);
   }
 
-  function () payable external {}
+  event Received(address, uint);
+  receive() external payable {
+      emit Received(msg.sender, msg.value);
+  }
 }