What the renowned investor probably didn’t anticipate was that Musk, a fellow multi-billionaire, would interpret his message as a dare.

Buffett, whose Berkshire Hathaway owns See’s Candies, was responding to a shareholder’s question about whether he agreed with Musk’s views about so-called economic “moats,” a term Buffett coined in a 1999 Fortune article referring to a company’s wide competitive advantages.

While Buffett has long extolled the benefits of moats—which are a key component of his stock-picking process—Musk spurned the concept entirely during a Tesla earnings call this week.

“I think moats are lame,” Musk told analysts on Tesla’s first-quarter earnings call Wednesday. “They are like nice in a sort of quaint, vestigial way. If your only defense against invading armies is a moat, you will not last long. What matters is the pace of innovation, that is the fundamental determinant of competitiveness.”

Presented with Musk’s comment, Buffett acknowledged that the acceleration of technological advancement in recent years has made more moats vulnerable and “susceptible to invasion.” But he still believes the concept is crucially important, and that some companies’ moats are more impenetrable now than they’ve ever been.

“Certainly you should be working on improving your own moat and defending your own moat all the time. And Elon may turn things upside down in some areas,” Buffett said during the Berkshire meeting in Omaha. “I don’t think he’d want to take us on in candy.”

Buffett often cites See’s Candies as a company with a wide moat, because of the company’s loyal, entrenched customer base, particularly on the West Coast—making it difficult for any rival chocolate chains to steal any business from See’s.

Berkshire Hathaway acquired See’s Candies in 1972, and Buffett is famously fond of its peanut brittle— which he and his business partner Charlie Munger continuously munch on while answering questions for six hours at their shareholder meeting each year. Some of Berkshire Hathaway’s other businesses also have moats wide enough to stave off competition from an innovative tech upstart, such as Garanimals, a line of children’s clothing it owns, Buffett added.

Munger also scoffed at Musk’s perspective on moats. “Elon says a conventional moat is quaint, and that’s true of a puddle of water. And he says that the best moat would be to have a big competitive position, and that is also right,” Munger said. “It’s ridiculous. Warren does not intend to build an actual moat. Even though they’re quaint.”

Musk, who did not attend the Berkshire Hathaway meeting, caught wind of Buffett and Munger’s comments, and apparently felt he was being trolled. Responding to the Berkshire Hathaway executives in a series of tweets, Musk first posted a musical YouTube clip from the movie Trolls.

Then Musk announced on Twitter, “I’m starting a candy company and it’s going to be amazing.”

I am super super serious

— Elon Musk (@elonmusk) May 5, 2018

Cryptocandy

— Elon Musk (@elonmusk) May 5, 2018

Although the Tesla CEO insisted he was “super super serious,” the tone of his Twitter thread — in which he also noted that “the plot of Willy Wonka is really messed up” — suggested otherwise. Still, Musk added, “Ok ok, just for sake of argument, what do you wish for in candy?” He followed that up with a single-word tweet: “Cryptocandy.”

Both Buffett and Munger loathe cryptocurrencies, which the Berkshire CEO on Saturday predicted “will come to bad endings.”

Later in the evening, Musk referenced Buffett directly, tweeting that he was “going to build a moat and fill it with candy” in order to lure Berkshire Hathaway into investing in his confectionery venture.

Then I’m going to build a moat & fill it w candy. Warren B will not be able to resist investing! Berkshire Hathaway kryptonite …

— Elon Musk (@elonmusk) May 6, 2018

As for whether the investing duo will respond to Musk, it’s unlikely they even took notice of his tweets: While Buffett has a Twitter account, he has tweeted exactly nine times, and not since the 2016 Berkshire Hathaway meeting two years ago.