Temporary workers at Walmart filed a class action lawsuit against the company and two staffing agencies yesterday, arguing that the retailer forced the temps to work longer hours without a lunch break. The suit alleges violations of federal minimum wage and overtime laws.

The lawsuit is a class action, but because it’s tied specifically to Labor Ready Midwest Inc. and QPS Employment Group, two staffing agencies, it appears to only affect temp workers at Walmart stores in the Chicago area. That would limit its impact to hundreds of temp workers; Walmart employes 1.4 million associates in the United States, roughly 1% of the total overall workforce. The suit was filed in federal court in Chicago.

The lawsuit comes amid one of the first serious backlashes by Walmart employees against the company in its history. This fall has already seen the first labor actions against Walmart ever, with strikes in 12 states. OUR Walmart, the non-union coalition of Walmart workers, plans further action in the months ahead, particularly on the post-Thanksgiving Black Friday, the most critical retail shopping day of the year. OUR Walmart opposes not just wage and hour restrictions, but the retaliation Walmart imposes on any worker for speaking out. OUR Walmart is backed by the United Food and Commercial Workers union, but is not seeking union recognition, preferring to act as a labor association, a throwback to similarly situated groups in the 1930s.

In this sense, the lawsuit can be seen as part of a continuing series of actions against Walmart, designed to both raise pressure and exact tangible changes to the company’s labor practices.

Walmart already settled dozens of similar wage and hour claims in 2008, paying $640 million. But the Supreme Court lent a hand to Walmart last year, arguing that a gender discrimination lawsuit, which included pay equity, could not proceed as a class action. It’s unclear how that ruling will affect this case.