Here’s a good reminder of why you should always read nutrition labels carefully: Cheerios Protein, a protein-boosted version of General Mills’ classic cereal, is the subject of a lawsuit for alleged false advertising and misleading labeling. The suit, filed by the consumer advocacy group Center for Science in the Public Interest (CSPI), claims that the cereal has only “negligibly” more protein than regular Cheerios but substantially higher levels of sugar.

According to CSPI and the cereals’ nutrition labels, Cheerios Protein has seven grams of protein per serving, while regular Cheerios has three grams. But a serving size of Cheerios protein is 55 grams, while the serving size of plain old Cheerios is 28 grams. In addition, the protein-packed cereal has 17 grams of sugar, while the classic variety has just one gram.

“Consumers who buy Cheerios Protein probably think they’re doing themselves a favor, and that this more expensive product is essentially a protein-fortified version of original Cheerios,” CSPI Litigation Director Maia Kats said in an online statement. “In fact, the main thing that distinguishes Cheerios Protein from original Cheerios is the huge amount of sugar and extra calories.”

In an e-mailed statement to BuzzFeed, General Mills spokesman Mike Siemienas noted that “[a]n equal amount of Cheerios Protein contains 18 percent more protein by weight than original Cheerios.” He also noted that the amount of protein in Cheerios Protein meets the Food and Drug Administration’s requirement for claims that a food is a “good source” of a nutrient—which is that it must contain 10 to 19 percent of a daily recommended value of that nutrient. Cheerios Protein contains 10 percent of that recommended daily value for protein.