What Americans don’t know about their retirement needs could hurt them—but what they think they know could hurt them more, according to a new survey.

Almost two-thirds of Americans say they’re not concerned about running out of money in retirement, according to the 2016 TIAA Lifetime Income Survey.

The survey reflects a general optimism among U.S. households—65 percent of the respondents were unconcerned about a retirement shortfall—but TIAA’s chief income strategist, Diane Garnick,  says the results likely reflect a population in denial about their personal finances.

“That means that only 35 percent are concerned about running out of money in retirement, and we think those numbers should be completely opposite—two-thirds of us should be worried while one-third of us shouldn’t be,” Garnick says. “There’s a huge disconnect. Because we’re living longer and because the do-it-yourself saving strategy isn’t working like it was expected to, I think it’s more likely that 65 percent of Americans are living in denial.”

Still, most respondents, 58 percent, felt confident that they could successfully generate income from their savings during their retirement.

Other survey responses suggest that these respondents are also in denial. Just 46 percent of respondents knew how much they have saved in their retirement accounts, and fewer, 35 percent, know how much income they’ll be able to generate each month in retirement.

“We kind of saw this at the end of the financial crisis in 2008, people were suffering from the five stages of economic grief and stage one was denial,” Garnick says. “How many people decided that they didn’t even want to open their retirement account statements anymore? They didn’t even want to know what the balance is.”

Americans seem to harbor mistaken assumptions about retirement, according to TIAA. Most of the survey’s respondents, 63 percent, assumed that they’re going to need less than 75 percent of their current income to live comfortably in retirement, yet TIAA claims that most experts believe that retirees will need to replace 70 to 100 percent of their retirement income.

“I think people are able to intellectually recognize that they have a personal retirement problem, but until they are able to emotionally acknowledge that this is a problem that needs an immediate fix, they’re able to remain in denial,” Garnick says. “People are naturally afraid of complexity, so they take mental shortcuts.”

When asked what they were looking for from a retirement plan, nearly half of the respondents, 49 percent, said lifetime income to cover their costs of living and another 24 percent said protection from market volatility.