Heritage Foundation scholar Robert Rector said Monday that his $6.3 trillion estimate of the cost of legalizing the illegal immigrations in America today is likely an underestimate.

“I believe that this cost estimate of $6.3 trillion is in fact a very, very low estimate. It assumes that there are only 11.5 million illegal immigrants in the United States, I believe the actual number is considerably higher than that,” Rector, the lead author of the Heritage report on the cost of mass legalization, said during a press conference.

“It also assumes there will be no cheating, in terms of people applying for and receiving amnesty, who do not in fact deserve it,” he added. “In the 1986 amnesty, probably 25 percent of the people who received amnesty were in fact not eligible.”