Betterment CEO Jon Stein.

Robo-advisors haven’t had much experience with market routs. When confronted with one on Monday, they struggled.

The websites of two of the country’s biggest robo-advisors — Wealthfront Inc. and Betterment LLC — crashed as the S&P 500 Index sank 4.1%. Complaints quickly spread across Reddit and other internet sites from people who had trouble logging onto their accounts. “Really?” wrote @jlpatel23 after he received a message from Wealthfront saying its site was down.

The glitches represent a setback for a niche of the financial market industry that has been booming of late as people have become more comfortable making investment decisions without speaking to human advisors.

Wealthfront acknowledged in a statement that its clients lost access to their accounts for “a short period of time today” and said it was’ working to ensure that “clients don’t experience this again.”

Betterment didn’t immediately respond to requests for comment.

Back in June 2016, during the Brexit fallout, Betterment had told users that it instituted a “short delay in trading” to protect its users from a “potentially erratic market.” No such statement was issued by the company in this case.

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