Elon Musk sold at least $3.6 billion worth of Tesla shares during trading this week. The eye-popping total increases the total value of shares he has sold this year to $23 billion. The sale comes despite Musk’s promise, in April, to stop selling off shares.

The billionaire’s need for liquidity stems from his acquisition of Twitter, which carries billions in debt, including some $13 billion in debt resulting from the acquisition itself.

Tesla stock is down more than 60% from its all time high, underperforming the broader market.