Republican presidential frontrunner Donald Trump mixed up the name of a key endorser with that of one of his rival’s top backers while campaigning in upstate New York Tuesday afternoon.

Speaking to a crowd in Rome, N.Y., ahead of next week's Empire State primary, Trump was listing a number of key individuals who have endorsed his campaign when he mentioned “Bob Vander Plaats from Liberty University.”

However, Vander Plaats, the CEO of the Iowa-based socially conservative ‘Family Leader’ organization, is actually the national co-chair of Texas Sen. Ted Cruz’ presidential campaign.

“[Phoenix-area] Sheriff Joe Arpaio endorsed me…[New Jersey Gov.] Chris Christie and Sarah Palin—Bob Vander Plaats from Liberty University,” the New York real estate mogul said.

Trump apparently meant to give a nod to the Rev. Jerry Falwell, Jr., president of the prominent Christian university in Lynchburg, Va., and an early backer of his presidential bid.

Vander Plaats later responded to Trump’s mix-up on Twitter, writing “So sorry, @RealDonaldTrump, I’m “Cruzin” to the nomination with @tedcruz. No interest in “Art of the Deal”,” referencing Trump’s 1987 bestselling book.