Elon Musk is telling investors not to borrow against the securities they own, saying it could case “mass panic” in the stock market, Bloomberg reports.

Ironically, this is exactly what Musk did—assume $13 billion in debt—when he purchased Twitter. The investment banks that worked with Musk on the $44 billion deal are now looking to restructure some of that high-interest debt with margin loans backed by Tesla stock that Musk would personally be on the line to repay.

Throughout this year, Musk has sold nearly $40 billion of his Tesla shares (TSLA), which has contributed to the stock trading at a two-year low.

In December 2020, Musk pledged 92 million Tesla shares as collateral to build his gigafactory in Shanghai, an April 2022 SEC filing shows.

“I would really advise people not to have margin debt in a volatile stock market, and, you know, from a cash standpoint, keep powder dry,” Musk said during an All-In podcast that aired Friday. “You can get some pretty extreme things happening in a down market.”

Musk also said, once again, the economy may be headed for a recession, potentially on the scale the U.S. endured in 2009: “My best guess is that we have stormy times for a year to a year and a half, and then, dawn breaks roughly in Q2 2024. That’s my best guess,” Musk said.

“Booms don’t last forever—but neither do recessions.”