After chastising bankers for failing to reward depositors, Italy has authorized a one-time 40% tax on the profits banks make from increased interest rates, in an unexpected decision that sent financial shares falling throughout Europe.

Sharply higher official interest rates have resulted in record profits for banks, as lenders raise lending rates while deferring payment on deposits.

Windfall taxes have already been levied on the industry in countries like as Spain and Hungary, and others may soon follow suit.

Italian Prime Minister Giorgia Meloni’s government had floated the idea of a windfall tax on banks earlier in the year but appeared to have cooled on the plan.

A senior banking executive told Reuters that lenders had been ready for “the chopping block, but then the axe didn’t come down.”

Since then, however, bumper first-half results from banks brought the issue starkly into focus once again and prompted the government to act on the eve of the summer political shutdown.

One source said the plan came as a surprise even to some ministers at Monday night’s cabinet meeting.

Italy’s banking share index plunged 7.4% by 0915 GMT on Tuesday, with top bank Intesa Sanpaolo (ISP.MI) down 8% and rival heavyweight UniCredit (CRDI.MI) down 6.5%. Italian banks dragged the European index (.SX7E) down 2.4%, with a Moody’s downgrade of some U.S. banks also weighing on bank shares.

“One has only to look at banks’ first-half profits … to realise that we are not talking about a few millions, but … of billions,” Deputy Prime Minister Matteo Salvini told a news conference in Rome late on Monday.