About a quarter of the distributors who received initial shipments of the experimental brew—a peachy Belgian lambic—returned them, the Dogfish Head Brewery founder recalls. Their complaint: “Hey, idiots, your beer went sour.”

(The acidity was, of course, intentional.)

Fifteen years later, sales are rising faster for sours than just about any other craft beer style, says Nielsen’s Caitlyn Battaglia. Wine drinkers—and women, in particular—appreciate the flavor, drawing a new set of drinkers into the $26 billion market for craft beer, says Bart Watson, chief economist at the Brewers Association.

Today Dogfish Head boasts America’s best-selling sour beer, bar none: SeaQuench Ale, a tripartite Kolsch, Gose, and Berliner Weisse. The tart tincture reaps two times more revenue than the category’s runner-up moneymaker, Victory’s Sour Monkey, and triple that of the next rival, Sierra Nevada’s Otra Vez, per IRI data.

If SeaQuench continues to swell at its current breakneck clip, the lime-and-salt-infused concoction will unseat Dogfish Head’s top-grossing beer, 60 Minute IPA, in 2021. In a world where “craft” and “IPA” have become nearly synonymous, that’s no small feat.

“In my 23 years as a professional brewer, I’ve never been more proud of a recipe,” Calagione tells Fortune.

Who knew sour could taste so sweet.