For DREAMers, Trump’s presidency could be a nightmare.

Almost a million undocumented immigrants who were brought to the U.S. as children trusted the federal government with their personal information—including their home addresses—so they could gain temporary protection from deportation.

But under the Donald Trump administration, that could make them targets; in a brutal twist of irony, their faith in American institutions could actually increase their risk of being forcibly removed from the country.

DREAMers are the undocumented immigrants who came to the U.S. as minors, haven’t committed any crimes, and could get temporary work permits and protection from deportation through Obama’s Deferred Action for Childhood Arrivals program (known as DACA). Under the Obama presidency, DACA was a godsend; it meant DREAMers who built their entire lives in the U.S. could stay without fear. It made it easier for them to get jobs and plan their futures.

They trusted their government. And now, that government is about to change.

On the campaign trail, Trump made two big commitments regarding deportations: First, he consistently said that his top deportation priority would be undocumented immigrants who have committed crimes—a priority shared by his predecessor, President Obama. And second, Trump said over and over and over that undocumented immigrants who entered the U.S. legally but then stayed longer than their visas allowed would also be deported.

In an address on Aug. 31, 2015, where he first outlined his vision for immigration policy, he emphasized that point.

“Removing visa overstays will be a top priority of my administration,” he said. “If people around the world believe they can just come on a temporary visa and never leave—the Obama-Clinton policy—then we have a completely open border. We must send the message that visa-expiration dates will be strongly enforced.”

It isn’t clear if Trump would direct Immigration and Customs Enforcement to actively track down the 4 million or so undocumented immigrants who came to the U.S. legally and then overstayed.

And that has DREAMers and their attorneys deeply worried. That’s because in order to get protected from deportation through DACA, DREAMers had to apply with the Department of Homeland Security. To apply, they had to give the DHS their current home address as well as proof that they had lived in the U.S. (illegally) for at least five years.

For many DACA applicants, that meant giving DHS a document showing their initial, now-expired visas, called an I-94.

“On that document, it specifically states when you were supposed to have departed,” explained Matthew Kolken, an immigration attorney. “That would be proof that you were a visa overstay.”

Kolken told The Daily Beast that he advised most of his clients against applying for DACA because he worried an administration hostile to undocumented immigrants could use the information they turned over against them.

“It puts a target on your back,” he said. “There is absolutely no way to predict what Donald Trump or anyone else would do.”

In previous years, many immigration attorneys encouraged their clients to take the risk and apply for DACA protection.

But that protection wasn’t permanent, and Trump has promised to eliminate it on his first day in the Oval Office.

It’s unclear what, if anything, DHS will do with the personal information it has on the 728,000 people enrolled in DACA. Kolken said DACA recipients shouldn’t panic, especially since Trump hasn’t specifically said he would target DACA participants for deportation.

“But who knows what he’s going to do?” he added.

Bryan Johnson, an immigration attorney who primarily works with children, said the top immigration advisers on Trump’s transition team—Kansas Secretary of State Kris Kobach and Alabama Sen. Jeff Sessions—concern him. Kobach and Sessions are two of the GOP’s most dogged immigration hawks, pushing tirelessly for tighter restrictions on legal immigration and much stricter enforcement of current laws.

“There’s a good chance that if Trump follows them and gives them a lot of autonomy, the whole focus on criminals is going to be a façade,” Johnson said. “They’re really going after all immigrants.”

For the time being, Johnson said he can’t offer much comfort to DACA participants.

“There’s not much to tell them except for, maybe, move your address,” he said. “On the safe side, I would tell them to relocate, just until we know what’s going on.”

Reached for comment on this story, a DHS official said he didn’t want to speculate on what President-elect Trump will do with the information he has about DACA recipients.

The uncertainty about the future is all too real for Juan Escalante, whose parents brought him to the U.S. from Venezuela when he was 11. His family came here legally, but their immigration attorney gave them bad advice: to let their visas expire while they were applying for green cards. As a result, Escalante and his family lost their legal status. Escalante hasn’t been able to get a green card since then. He is enrolled in the DACA program, and worries that if Trump eliminates it, he could lose his job or even face deportation.

“My name could potentially show up on a list,” he said. “And that’s a threat that I’m operating with.”