Kraft secretly changed the recipe for its classic Kraft Macaroni & Cheese—and no one could tell the difference, Fortune reports. Since adjusting the formula in December, the food company has sold more than 50 million blue boxes of the new recipe without even hinting that it’s different in its advertising or with its packaging.

The reason for the change is simple: Kraft felt threatened by other popular instant macaroni and cheese dinners on the market, like Annie’s Homegrown, which offers nearly two dozen varieties of boxed macaroni and cheese, all of them made with real cheese and no artificial preservatives or flavors. Now Kraft can make the same claim. The new recipe is more natural, as Kraft replaced artificial ingredients and synthetic colors with paprika and turmeric to maintain the product’s iconic bright orange color. Kraft also stopped using artificial flavors and preservatives.

“We knew the new product tasted just as good as the old, exactly in line with what fans had expected,” Greg Guidotti, vice president of meals at Kraft Heinz told Fortune. “We wanted fans to experience that new recipe for themselves without being prompted.”

[h/t Fortune]