Former Federal Reserve Chairman Jerome Powell on Sunday warned against politicizing the central bank, amid concerns President Donald Trump is undermining the institution’s prized independence. Powell’s speech while accepting the John F. Kennedy Profile in Courage Award in Boston came after he suggested that the Justice Department’s investigation into concerns he lied or misrepresented the taxpayer-funded, multibillion-dollar renovation of the Fed headquarters building in Washington was politically motivated. This week, Powell reiterated his call for officials to respect the central bank’s independence, saying that “like many other institutions, the Fed has been undergoing a stress test,” during one of his first major public appearances since leaving office.

“Congress wisely chose to insulate monetary policy decisions from political pressure. All other advanced economy nations have done the same,” Powell said during remarks at the John F. Kennedy Presidential Library.

“Democratic institutions take much time, effort, and patience to build but can be torn down all too quickly,” he added. “It is essential that we preserve what is good about ⁠these institutions, even as we strive to improve them.”