Sergio Carillo, a landscape contractor in Rialto, California, will get $20,000 in a settlement following his arrest by U.S. Immigration and Customs Enforcement.

Carillo has been a U.S. citizen since 1994, but was arrested by immigration officials in July 2016. Although he claimed citizenship, Carrillo was detained for three days and finally released after the providing documentation of his passport and certificate of citizenship to an ICE agent.

Feeling that his rights were violated, Carillo and the American Civil Liberties Union sued, alleging that ICE agents ignored his pleas that he was an American citizen. “I think it’s particularly alarming that they never took any steps to investigate his citizenship,” said attorney Jennie Pasquarella, the ACLU of California’s director of immigrants’ rights.

Pasquarella said that Carillo repeatedly claimed he was a U.S. citizen. ICE’s policy is to promptly investigate such claims. Carillo was born in Mexico, but didn’t show up in immigration databases.

According to ICE spokeswoman Lori Haley, the agency cannot release specific information about a U.S. citizen. “ICE would never knowingly take enforcement action against or detain an individual if there was probative evidence indicating the person was a U.S. citizen,” Haley wrote, via email.

Federal attorneys and the ACLU reached the $20,000 settlement on Carrillo’s behalf on November 29, 2017.