The Supreme Court on Wednesday wrestled with the meaning of the word “file” in a job retaliation case with potentially huge ramifications for workers who allege wage-and-hour violations by their employers.

Kevin Kasten sued his former employer, Saint-Gobain Performance Plastics Corp., alleging that it fired him in retaliation for a series of verbal complaints about the illegal location of time clocks in his factory. A federal district court and the 7th U.S. Circuit Court of Appeals ruled against him, holding that the anti-retaliation provision in the Fair Labor Standards Act protects internal complaints only if they are written.