Chick-fil-A is launching a new gluten-free bun option across the United States this month, the fast food chain announced Monday.

The new bun is made from quinoa and amaranth, and slightly sweetened with molasses and raisins, the company said in a statement. It contains 150 calories and costs an extra $1.15. Customers with gluten-free dietary needs are advised to assemble their own sandwiches in order to reduce cross-contamination risks.

Before launching the menu addition across the country, Chick-fil-A has been testing the bun in Washington state, Idaho and Mississippi since April 2016, according to a report by Gluten-Free Living. While the option remains rare in the fast-food industry, Chick-fil-A is not the first to offer gluten-free buns. Shake Shack and Red Robin have similar options. McDonald’s restaurants in the Netherlands are testing gluten-free buns as well, according to NBC.

There are at least three million of Americans with celiac disease, a condition that leads to damage in the small intestine when patients consume gluten, according to the Celiac Disease Center at the University of Chicago Medicine. There are another estimated 18 million people with non-celiac gluten sensitivities, according to Beyond Celiac.

But people may be sticking to the gluten-free diet more than necessary. A JAMA Internal Medicine study in 2016 found that one in five people in the country avoids gluten, even though celiac disease is estimated to affect only 1% of the population.