Regulators are starting to freak out a little over what will happen in U.S. financial markets in 2021 when a major benchmark interest rate is expected to vanish.

The Securities and Exchange Commission recently issued guidance to registrants telling them preparing for new reference rates to underpin trillions of dollars in financial contracts is becoming a matter of some “urgency.” Commission staff is “actively monitoring the extent to which market participants are identifying and addressing these risks,” the guidance says.