RadioShack’s calculation of overtime for certain employees violates Pennsylvania law, a federal judge has ruled in an opinion that adds to a recent series of decisions establishing the direction of overtime law as moving in workers’ favor.

The system RadioShack used to determine the amount of overtime pay due to salaried employees was the fluctuating workweek method, which grew out of the federal Fair Labor Standards Act and offers a way to calculate overtime pay to workers who aren’t paid hourly.