            } else {
                ERC20(order.baseAsset).safeTransferFrom(msg.sender, address(this), order.strike);
            }
    function exercise(Order memory order, uint256[] calldata floorAssetTokenIds) public payable {
        ...

        if (order.isCall) {
            // -- exercising a call option

            // transfer strike from exerciser to putty
            // handle the case where the taker uses native ETH instead of WETH to pay the strike
            if (weth == order.baseAsset && msg.value > 0) {
                // check enough ETH was sent to cover the strike
                require(msg.value == order.strike, "Incorrect ETH amount sent");

                // convert ETH to WETH
                // we convert the strike ETH to WETH so that the logic in withdraw() works
                // - because withdraw() assumes an ERC20 interface on the base asset.
                IWETH(weth).deposit{value: msg.value}();
            } else {
                ERC20(order.baseAsset).safeTransferFrom(msg.sender, address(this), order.strike);
            }

            // transfer assets from putty to exerciser
            _transferERC20sOut(order.erc20Assets);
            _transferERC721sOut(order.erc721Assets);
            _transferFloorsOut(order.floorTokens, positionFloorAssetTokenIds[uint256(orderHash)]);
        }
            if (weth == order.baseAsset && msg.value > 0) {
                // check enough ETH was sent to cover the premium
                require(msg.value == order.premium, "Incorrect ETH amount sent");

                // convert ETH to WETH and send premium to maker
                // converting to WETH instead of forwarding native ETH to the maker has two benefits;
                // 1) active market makers will mostly be using WETH not native ETH
                // 2) attack surface for re-entrancy is reduced
                IWETH(weth).deposit{value: msg.value}();
                IWETH(weth).transfer(order.maker, msg.value);
            } else {
                ERC20(order.baseAsset).safeTransferFrom(msg.sender, order.maker, order.premium);
            }
        // filling short call: transfer assets from maker to contract
        if (!order.isLong && order.isCall) {
            _transferERC20sIn(order.erc20Assets, order.maker);
            _transferERC721sIn(order.erc721Assets, order.maker);
            return positionId;
        }
            } else {
                ERC20(order.baseAsset).safeTransferFrom(msg.sender, address(this), order.strike);
            }
        // transfer assets from putty to owner if put is exercised or call is expired
        if ((order.isCall && !isExercised) || (!order.isCall && isExercised)) {
            _transferERC20sOut(order.erc20Assets);
            _transferERC721sOut(order.erc721Assets);

            // for call options the floor token ids are saved in the long position in fillOrder(),
            // and for put options the floor tokens ids are saved in the short position in exercise()
            uint256 floorPositionId = order.isCall ? longPositionId : uint256(orderHash);
            _transferFloorsOut(order.floorTokens, positionFloorAssetTokenIds[floorPositionId]);

            return;
        }
            } else {
+               if (order.strike > 0) {
                    ERC20(order.baseAsset).safeTransferFrom(msg.sender, address(this), order.strike);
+               }
            }
