Imagine you are at the ice-cream shop, an array of colorful flavors lie before you in a glass case. A flavor calls to you, its label reads “pistachio”.

After your purchase, you look online at the ice-cream shop’s website. Turns out, the pistachio ice-cream had no pistachios in it. Instead, it had “pistachio flavoring”, made up of “water, ethanol, propylene, glycol, natural & artificial flavor, yellow 5 [and] blue 1”.

So what do you do? You gather other ice-cream aficionados and sue the ice-cream company.

That’s what a Long Island woman did after ordering the pistachio ice-cream in July 2022 at a Cold Stone Creamery and realizing the ice-cream was devoid of pistachios.

While the class-action suit has yet to go to court, Gary Brown, a federal judge at the eastern district court of New York in Brooklyn, is allowing the case to move forward. The suit targets Kahala Brands, the parent company of Cold Stone Creamery.

In a ruling last week, the judge appeared sympathetic to the woman’s claims that Cold Stone Creamery misled her and other customers by not including pistachios in what the company calls pistachio ice-cream.

“Had she known that the product did not contain pistachio, she would not have purchased it, or would have paid significantly less for it,” lawyers for the woman wrote in court filings.

The judge wrote that the case presented a “deceptively complex question about the reasonable expectations” of those who find themselves with such an ice-cream flavor.

“Should consumers ordering pistachio ice-cream at one of defendant’s establishments expect that the product will contain actual pistachios? And if the answer is no, should that leave them with a bitter aftertaste?” Brown wrote.

The judge at least agrees the question is worth sussing out in court, at least when it comes to the pistachio flavor. While the lawsuit named other alleged deceptive ice-cream flavors, including mango, coconut, mint, orange, orange sorbet and butter pecan, Brown said the lawsuit moving forward can only focus on pistachio, as it only brought forward sufficient evidence for that flavor alone.

Brown noted that lawyers for Cold Stone cited the logic behind the so-called “vanilla cases”, or a series of lawsuits that were dismissed by the southern district court of New York that claimed items that were labeled as vanilla, but did not actually contain vanilla bean as an ingredient.

But the judge said the term vanilla can be both a noun and an adjective, sometimes being used to denote a flavor rather than the physical vanilla bean. For example, you can have “vanilla-scented candles and shampoos”. But the dictionary defines pistachio as a noun, describing the actual nut in question.

Brown also scoffed at Cold Stone’s defense that its listing of its ingredients on its website is enough cause for dismissal. “It seems inconceivable that such a consumer should have to search online to find the relevant webpages while waiting in line to order a scoop of ice-cream,” Brown wrote. “Before advancing this argument, counsel may be well-advised to research the term ‘buzzkill’.”

It is unclear when the case will go to trial. Kahala Brands did not immediately respond to the Guardian’s request for comment.