Elon Musk bought 13,037 Tesla Inc. shares for $10 million on February 14, according to a filing with the U.S. Securities and Exchange Commission.

Musk purchased the shares at an average of $767 each, raising his holding to 34.1 million, or 18.5% of the Palo Alto-based company. Tesla’s shares have soared more than doubled this year and closed at a record high of $917.42 on Wednesday.

The rally, initially fuelled by a surprise third-quarter profit, has left Tesla with a market value greater than that of General Motors Co., Volkswagen AG and Fiat Chrysler Automobiles NV combined. Traders are realizing the dangers of betting against the company: roughly 15% of its shares available for trading are short, the lowest in at least a year, according to S3 data.

Musk was in Shanghai at the start of the year to open Tesla’s first manufacturing facility outside the U.S. The coronavirus outbreak in China led to a halt in production at the facility, though operations restarted last week.