Recently, Coca-Cola changed the color of some of its bottle caps from red to yellow, confusing many people.

The company has implemented a notable change in design for a very specific reason- to distinguish bottles of Coca-Cola that are kosher for Passover. These yellow-capped bottles contain Coca-Cola that follows the dietary restrictions set in place for this holiday.

“Passover” or “Pesach” is a Jewish holiday that takes place in March or April, depending on the lunar calendar. This week-long celebration is for Jews to recall Moses’ life and the Exodus of his people from Egypt. In remembrance of the Jewish people who fled the pharaoh and didn’t have time to wait for the bread to rise, or leaven, during Passover, Jews refrain from eating leavened foods.

They avoid foods derived from wheat, oats, spelt, barley, and rye during the week before Passover. In fact, crumbs of leavened items in some Jewish households must be completely removed from the pantry and cupboards.

Many Ashkenazi Jews, like their ancestors before them, do not consume corn or corn by-products during Passover. It has long been prohibited for Jews to consume corn, rice, legumes, and seeds throughout the week of Passover.

Recently, the Committee on Jewish Law and Standards has allowed people to eat corn, rice, beans, and other legumes during Pesach. Some Ashkenazi Jews still don’t consume these foods during Pesach though. Consequently, any food that contains corn or corn by-products (like high-fructose corn syrup) is not permitted to be eaten.

Coca-Cola beverages include high-fructose corn syrup. That is why during Passover, Jews are forbidden to consume this ice-cold treat. Because Coca-Cola is produced with a barley enzyme, Jews who observe the Passover avoid drinking it.

This is why Coca-Cola has started using yellow-capped bottles. This is a reminder to everyone that the Coke in the bottles with yellow caps was produced without high-fructose corn syrup or alpha-amylase derived from barley. The firm has instead utilized sucrose or cane sugar in making these unique Coca-Colas.

The red caps on Coca-Cola bottles are so ubiquitous that we might not even notice the yellow-capped bottles unless we’re looking for them.

A Coke shopper went to Reddit and posted a picture of a yellow-topped Coca-Cola bottle set among red ones. If you take a closer look, you’ll see that the label is also slightly different and says “Original Taste.”

It starts by noting how Coca-Cola began releasing a kosher version of their top product in the 1930s, according to a short video shared by Business Insider’s Twitter feed. This Coke recipe is similar to the “Mexican Coke” in glass bottles and has a greater markup than standard Coca-Cola beverages.

The Passover Coca-Colas, on the other hand, are priced similarly to ordinary Cokes. They may have been produced with sugar rather than high-fructose corn syrup, but the cost is the same.

Make sure to buy the sugar cane version of Coca-Cola next time you see it! It’s easy to spot because of the yellow caps.