diff --git a/contracts/UniswapV2ERC20.sol b/contracts/UniswapV2ERC20.sol
index b925ffb..1c8b89d 100644
--- a/contracts/UniswapV2ERC20.sol
+++ b/contracts/UniswapV2ERC20.sol
@@ -74,19 +74,12 @@ contract UniswapV2ERC20 is IUniswapV2ERC20 {
         return true;
     }
 
-    function permit(
-        address owner, address spender, uint value, uint nonce, uint deadline, uint8 v, bytes32 r, bytes32 s
-    )
-        external
-    {
-        require(nonce == nonces[owner]++, "UniswapV2ERC20: INVALID_NONCE");
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
         require(deadline >= block.timestamp, "UniswapV2ERC20: EXPIRED");
-        require(v == 27 || v == 28, "UniswapV2ERC20: INVALID_V");
-        require(s <= 0x7fffffffffffffffffffffffffffffff5d576e7357a4501ddfe92f46681b20a0, "UniswapV2ERC20: INVALID_S");
         bytes32 digest = keccak256(abi.encodePacked(
             "\x19\x01",
             DOMAIN_SEPARATOR,
-            keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonce, deadline))
+            keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))
         ));
         address recoveredAddress = ecrecover(digest, v, r, s);
         require(recoveredAddress != address(0) && recoveredAddress == owner, "UniswapV2ERC20: INVALID_SIGNATURE");
diff --git a/contracts/interfaces/IUniswapV2ERC20.sol b/contracts/interfaces/IUniswapV2ERC20.sol
index fa1f5d4..b3ba001 100644
--- a/contracts/interfaces/IUniswapV2ERC20.sol
+++ b/contracts/interfaces/IUniswapV2ERC20.sol
@@ -19,8 +19,5 @@ interface IUniswapV2ERC20 {
     function PERMIT_TYPEHASH() external pure returns (bytes32);
     function nonces(address owner) external view returns (uint);
 
-    function permit(
-        address owner, address spender, uint value, uint nonce, uint expiration, uint8 v, bytes32 r, bytes32 s
-    )
-        external;
+    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
 }