Former Rep. Beto O’Rourke (D-TX) and ex-Secretary of Housing and Urban Development Julian Castro sparred over immigration on Wednesday, specifically whether it should be a crime to enter the U.S. illegally without papers.

At the first Democrat presidential debate, O’Rourke was asked what he would do on his first day in the White House by one of the event’s moderators, José Díaz-Balart. After giving the first portion of his answer in Spanish, O’Rourke switched back to English to explain he would reform the nation’s border entry law.

“We would not turn back Valeria and her father Oscar,” the former congressman said, citing two immigrants who recently died at the U.S.-Mexico border. “We would accept them into this country and follow our own asylum laws. We would not build walls, we would not put kids in cages.”

As O’Rourke was speaking, Castro interjected to say the only reason “they were separating children from their families was because of Section 1325 of the Immigration and Nationality Act. The section in question makes it misdemeanor  for immigrants to enter the U.S. without papers.

“Let’s be very clear, the reason that they are separating these little children from their families is that they are using section 1325 of that act, which criminalized crossing over the border, to incarcerate the parents and then separate them,” Castro said. “Some of us on this stage have called to end that section, to terminate it, some, like Congressman O’Rourke, have not.”

“I want to challenge all of the candidates to do that,” Castro continued. “I just think it’s mistake, Beto. I think it’s a mistake. If you truly want to change the system, then we have to change that system. If you don’t, then it might as well be the same policy.

O’Rourke attempted to defend himself by saying that he had helped to introduce legislation as a member of Congress to ensure that those seeking asylum and refuge aren’t criminalized.

“If you’re fleeing desperation then I want to make sure you’re treated with respect,” O’Rourke said.

Castro shot back that wasn’t the type of immigration he was discussing.

“I’m not talking about the ones that are seeking asylum,” he said. “I’m talking about everyone else… I’m talking about millions of folks, a lot of folks that are coming are not seeking asylum, a lot of them are undocumented immigrants.”

The former secretary said O’Rourke was wrong to worry about the impact repealing the section would have on human trafficking, as that was already a crime in another section of the legal code.

“I think you should do your homework on this issue,” Castro said. “If you did your homework on this issue you would know that we should repeal this section.”

Since announcing his candidacy, Castro has advocated for making entering the country illegally a civil violation, rather a criminal one.