Be on the lookout next time you go to the gas station. Naturally, the first thing you’re probably going to look at when you pull up is the current cost of unleaded. But there’s one other thing you should get eyes on, as well. Police departments across the country are warning drivers about a new gas pump scam called the “screw method.” This deceptively simple scam can fleece you of hundreds of bucks using (you guessed it) a screw.

It works like this: Fraudsters stick a screw into the nozzle cradle of the gas pump, positioning it so that the lever never fully returns to the off position after you’re finished fueling up. That way, there’s no signal to end the transaction. The pump shuts off, you drive off, but the transaction is still active. Then the scammer can just pull up to your pump and start filling up their tank (and, maybe even some additional gas canisters) on your dime.

In a way, it’s kind of like an automated version of the tried-and-true pump-switching gas station scam. Authorities have issued warnings about the scam in multiple states, including California, Maryland, Pennsylvania, and Texas; it’s a coast-to-coast conundrum. Your best defense is paying close attention before, during, and after fueling. Take a minute to inspect the nozzle cradle before you start your transaction. Look for anything unusual, including screws or other objects that could interfere with the pump. Don’t walk away from the pump while fueling up; someone could stick a screw in there while you’re gone.

Also, don’t just assume the transaction’s done just because you put the pump back. Once you’re done filling your tank, you should wait for the transaction to fully finish before driving away. The pump screen should either ask if you want a receipt or reset the total back to zero dollars and zero gallons. That’s your sign your card info’s safe.

You may want to review your card statements after, as well, just to be extra sure. You should also be on the lookout for your fellow filler-uppers’ sake: If you pull up to the pump and notice the transaction’s still active, do them a favor and flag an attendant to wrap things up for them.