Nikola’s stock fell. Founder Trevor Milton bought shares.

Alternative fuel truck company Nikola has seen its shares drop recently, but CEO Trevor Milton has just bought shares.

Nikola (NKLA) shares fell after a negative report of a short sale. Nikola refuted the charges Friday and Monday. Milton, who founded the company, said last week that Nikola’s shares are undervalued.

Milton paid $ 1.3 million on Monday for a total of 41,400 Nikola shares, an average price per share of $ 30.91 each. According to a form filed by Milton with the Securities and Exchange Commission, he made the purchases through M&M Residual, a limited company he owned. He remains Nikola’s largest shareholder through M&M, which now owns 91.6 million shares.

Last week a pact was made for General Motors (GM) to acquire an 11% stake in Nikola provided the latter with validation, while the former received an affirmation of its technology. When asked at a RBC Capital Markets virtual conference on Monday about the company’s transaction, CEO Mary Barra said that GM “has worked with many different partners and we are a very capable team that has done the proper due diligence.”