It was a call retired Lt. Gen. H.R. McMaster did not expect to receive.

McMaster, former national security adviser to Donald Trump in the president’s first administration who lasted less than a year into Trump’s term, answered his cell phone last month. Trump was on the other end of the line.

McMaster has been critical of the former president, and just a day before the call, Trump ripped him as a “weak and totally ineffective loser,” according to CBS News, which originally reported on the call, citing four unnamed sources.

“Henry,” Trump began the call.

But the “H” in McMaster’s first name is Herbert — he is called “H.R.” for Herbert Raymond, not Henry.

That’s when McMaster realized Trump did not intend to call him.

When McMaster identified himself, the president cursed out his former national security adviser to aides who mistakenly dialed his number.

“Why the f— would I talk” to H.R. McMaster? Trump asked before going into a “scathing critique of his former aide,” two sources told CBS News.

The sources said Trump intended to speak with South Carolina Gov. Henry McMaster, one of his staunchest supporters.

Sources told CBS News the call between Trump and H.R. McMaster was brief.

A Trump spokesman continued to bash H.R. McMaster to CBS News.

“H.R. McMaster has completely beclowned himself and his third-rate book, which is now sold in the bargain bin of the fiction section of a discount bookstore, is filled with lies in a futile attempt to rehabilitate his tattered reputation,” said White House communications director Steven Cheung.