Tesla CEO Elon Musk said that the carmaker plans to start building cars on its long-awaited next-generation vehicle platform starting next year. But he says it won’t be easy, and the timing isn’t set in stone. 

“Our current schedule says that we will start production towards the end of 2025, sometime in the second half,” Musk said on Tesla’s fourth-quarter earnings call on Wednesday. 

He warned that accelerating production on the new and “revolutionary” assembly line won’t be easy. 

“We really need the engineers to be living on the line,” he said. “This is not sort of an off-the-shelf, just works type of thing.”

Tesla’s upcoming platform will be built at its Texas factory to start and is expected to be the basis of a long-promised cheaper vehicle. That kind of addition to Tesla’s lineup is sorely needed for Tesla’s future growth. Just two models—the Model 3 sedan and Model Y SUV—account for nearly all of the company’s sales, while the new Cybertruck is expensive and unlikely to sell in huge volumes. Tesla needs a lower-priced, mass-market model to retain its competitive edge as rivals gain steam. 

Tesla’s first next-generation vehicle will be a compact crossover codenamed “Redwood,” Reuters reported on Wednesday. 

Musk doesn’t have the most stellar track record when it comes to sticking to deadlines, so we’ll have to see if the 2025 target holds. He first floated a plan for a $25,000 car in 2020, saying at the time that it would launch in three years. Tesla’s Cybertruck pickup launched in late 2023, years behind schedule. Its Roadster supercar is nowhere to be seen years after its public unveiling. 

Musk acknowledged during Wednesday’s call that Tesla could overshoot the 2025 goal: “I don’t want to blow your minds, but I’m often optimistic regarding time.”