Elon Musk just took another giant leap toward becoming the world’s first trillionaire. Earlier this month, Musk’s rocket maker SpaceX launched a tender offer valuing the firm at $800 billion, up from $400 billion in August, two of the company’s investors tell Forbes. That boosts the fortune of Musk, who owns an estimated 42% of SpaceX, by $168 billion to an estimated $677 billion as of 12 p.m. Eastern Monday. Musk is now the first person ever worth $600 billion or more. No one else has ever