Democrats want to tax stock buybacks to help pay for President Joe Biden’s $1.75 trillion spending plan. Billionaire investor Charlie Munger isn’t happy about it.

“I think it’s insane. Literally insane,” Munger, the right-hand man of legendary investor Warren Buffett, told CNN in an interview. The Build Back Better framework, released by the White House last week, promises the ambitious economic and climate agenda will be “fully paid for” in part by imposing a 1% surcharge on corporate stock buybacks. But Munger, the 97-year-old vice chairman of Buffett’s Berkshire Hathaway (BRKA), worries this plan represents a slippery slope.

“It’s so irrational, and I think it sort of destroys the whole system, once you start tinkering from Washington,” said Munger, who describes himself as a Republican. Companies frequently return extra cash to shareholders through dividends and stock buybacks. Wall Street loves buybacks because they simultaneously boost demand for shares and limit supply. They also inflate per-share profits, a key metric that drives stock prices. Added bonus: Buybacks can be turned on and off more easily than dividends.

Berkshire Hathaway (BRKA), Buffett’s holding company, spent $24.7 billion on stock buybacks last year alone. Under the Democrats’ proposed buyback tax, Berkshire would have owed $247 million to Uncle Sam on those purchases. “I don’t think the dividend policies of American corporations ought to be determined from Washington,” Munger told CNN. The Biden administration fired back after Munger’s criticism.