U.S. Senators today sent another letter to investment giant Fidelity Investments, warning it against offering Bitcoin to its customers following the collapse of crypto exchange FTX.

Senators Elizabeth Warren of Massachusetts, Tina Smith of Minnesota and Richard Durbin of Illinois all signed the letter asking Fidelity to scrap its 401(k) Bitcoin plan.

Today’s letter added that the U.S. was “already in a retirement security crisis” which “should not be made worse by exposing retirement savings to unnecessary risk.”