The Federal Trade Commission sued PepsiCo on Friday, alleging that it has engaged in illegal price discrimination by giving unfair price advantages to one large retailer at the expense of other vendors and consumers.

The Robinson-Patman Act was passed in 1936, but the federal government stopped enforcing it during the deregulation of the 1980s. The FTC resumed its enforcement in December when it sued Southern Glazer’s, the largest U.S. distributor of wine and spirits.

The US Federal Trade Commission sued PepsiCo Inc. Friday under a rarely invoked 1930s law called the Robinson-Patman Act that bars price discrimination against retailers.

A lawsuit filed by the Federal Trade Commission alleges that food and beverage maker PepsiCo engaged in illegal price discrimination by giving unfair price advantages to one big-box retailer

The FTC is suing PepsiCo for allegedly rigging the market by offering “unfair pricing advantages” that can contribute to inflation.

Company’s conduct has forced competing retailers, including convenience stores, to pay higher prices, agency says

According to the FTC’s complaint, Pepsi has been providing unfair pricing advantages to one of its largest customers—a major big box retailer—while raising prices for competing retailers and customers. Reuters reports that the retailer is none other than Walmart Inc. WMT , citing a source familiar with the discussions.

Walmart declined to comment. "The FTC's action will help ensure all grocers and other businesses — no matter the size — can get a fair shake and compete on the merits of their skill, efficiency, and talent,

The commission alleges that the retailer, whose name was redacted in the statement from commissioners, received “unfair pricing advantages” that were not made available to others.