U.S. Treasury Secretary Jack Lew cautioned on Monday against a false sense of complacency in the financial system just because it weathered the initial shock of Britain’s vote to leave the European Union.

“I’m very proud of the work that we’ve done on financial reform. I only hope that the fact that we’ve been able to withstand shocks, like the referendum here in the U.K., doesn’t make for a false sense of complacency,” Lew said.

“In the week after the British referendum I spoke to the heads of almost every big financial institution just to get their assessment of the impact and I don’t think any of them was sorry they had more capital,” Lew said in his remarks at the Oxford Union Society.

Mr. Lew added that he sees a fundamental threat to liberal democracy and free market capitalism if they do not work better for more people.

Lew added that an increasing number of people were feeling left behind economically and that inequality and the rise of populism was playing a role in the U.S. presidential election.