Federal Reserve Bank of Boston President Eric Rosengren warns that a relative calm in markets “may be challenged in the future” as the Fed reduces accommodation.

The sharp rise in interest rates last year is a reminder that “uncertainty or misunderstanding about the contours of our exit has the potential to be problematic,” Rosengren says in a speech in Guatemala City.

Recent low volatility in the U.S. Treasury market is due “in part to the very gradual and predictable reduction” in the Fed’s large-scale asset purchases, “along with an economy that has continued to improve, albeit only gradually and with some setbacks along the way,” he said. As part of an eventual reduction in stimulus, the Federal Open Market Committee could “decide to reinvest all but a given percentage of securities on the balance sheet as they reach maturity, and increase that percentage at each subsequent meeting:”

Rosengren does not vote on the FOMC this year.