Tesla CEO Elon Musk tweeted on Saturday that his company would cover any lost tax credit that a customer might incur if Tesla is late to deliver a promised vehicle.

In the US, drivers who purchase a battery electric vehicle qualify for a $7,500 Federal Tax Credit on the purchase of their vehicle—unless the automaker has sold more than 200,000 electric vehicles. Once that happens, customers of the automaker get two more quarters to qualify for the full credit, at which point the tax credit starts decreasing. Beginning January 1, Tesla customers will only receive a $3,750 credit.

Tesla customers generally place an order and then wait for a delivery time that could be days or weeks in the future. In mid-October, Tesla promised that any orders placed by October 15 would be delivered by the end of the year, thus qualifying for the full tax credit. Later, Tesla appeared to extend this deadline to November 30.

Now, Musk says that any missed deadlines on Tesla's part will have the lost $3,750 in federal tax credits compensated. "If Tesla committed delivery & customer made good faith efforts to receive before year end, Tesla will cover the tax credit difference," Musk tweeted in reply to a question about pre-December orders.

If Tesla committed delivery & customer made good faith efforts to receive before year end, Tesla will cover the tax credit difference — Elon Musk (@elonmusk) December 22, 2018

It's unclear how many vehicles this would apply to, since the customer would need to have received a promise of 2018 delivery and also made a good-faith effort to receive the car.

A day earlier, Musk tweeted that his company was reshuffling all cars destined to owners who can't take delivery before year's end, and also making test drive and display cars available for discounted sale. (According to GreenCarReports, Tesla said it would return the deposits of customers who ordered cars but couldn't receive them before the year's end).

Investors didn't much care for Musk's promise of a $3,750 discount on some late-delivered vehicles. CNBC reports that on Monday, Tesla stock slid nearly eight percent, possibly due to this news and news that Tesla is reducing the price of the Model 3 in China. Tesla reportedly said that it was "absorbing a significant part of the tariff to help make cars more affordable for customers in China." The base price for a Model 3 in China is now 499,000 yuan ($72,000).