The Department of Labor criticized Fidelity Investments’ plan to allow investors to put bitcoin in their 401(k) accounts.

“We have grave concerns with what Fidelity has done,” Ali Khawar, acting assistant secretary of the Employee Benefits Security Administration. Khawar stressed the speculative nature of cryptocurrency and the hype around the fear of missing out as reasons his department is concerned about the move. Khawar has said that crypto has “intriguing use cases” but needs “maturing” before it’s suitable to be placed into a retirement savings account.

The DOL cites crypto’s volatility, uncertain valuations, and evolving regulatory environment as reasons for concern.