Sweden’s biggest lenders said more than three years of falling interest rates have made the nation’s complacent about the risks of household debt costs, according to Bloomberg.

“The market is too heavily tilted toward three-month contracts,” said Ulrica Stolt Kirkegaard, the head of Svenska Handelsbanken’s Stadshypotek unit, the second-largest mortgage lender. “Not all Swedish households have a good enough economy for such a high share of flexible rates — there is too much optimism.”

The warning comes as the nation’s central bank is prepared to drive down long-term rates further, the newswire said. The Riksbank last year cut its benchmark rate to zero.