Tesla is hiking prices as it adds autopilot as standard on most of its cars. It’s also making it harder for customers to buy its cheapest model.

The company did not provide any specific reason for the changes announced on Friday, but it endured a tough 2018 after months of manufacturing hangups and delays in rolling out its best-selling Model 3.

“Autopilot is very important because our data strongly indicates that the chance of an accident is much lower when autopilot is enabled,” the company said in a statement.

“Autopilot also dramatically improves the quality of the driving experience, especially in heavy traffic, as thousands of our customers frequently describe online,” it added.