California’s push to electrify its cars is facing a potentially serious problem: People aren’t buying electric cars fast enough.

After three straight years of strong growth, sales have stabilized in California, raising questions about whether the state will fail to meet its groundbreaking mandate banning sales of gas-powered vehicles.

Douglas McIntyre, editor-in-chief at Climate Crisis 24/7, reports that EV sales in California—America’s largest EV market—grew by just 1% last year. With the state leading the push for EV adoption, this stagnation raises concerns for the rest of the country.