Musk is looking to put the two companies under one roof. Merger talks between SpaceX and Tesla have reached discussions on the stock-swap ratio and the governance structure of the combined company. An announcement could come as early as December, though it might be pushed to early next year. Based on Thursday’s closing prices, SpaceX is worth $1.9 trillion and Tesla $1.57 trillion—a simple sum of $3.47 trillion. That would make it the biggest deal in history, by a long shot.

The sticking point is the vote. Musk runs both companies, creating a conflict of interest, so a special committee is involved; ultimately, shareholders will decide. Tesla’s bar is high: the deal needs approval from holders of 50% of all outstanding shares—not just 50% of the shares represented at the meeting. The item isn’t even on the agenda for the annual shareholder meeting early next month.