Apple in a recent audit of its overseas manufacturing partners found that Hon Hai Precision Industry Co., part of Taiwan’s Foxconn Technology Group and the exclusive assembler of the iPhone X, employed high school students that worked for more hours than local laws permit.

Foxconn states that it doesn’t allow interns to work more than 40 hours per week on “program-related assignments.” However, in this instance, it admits that some interns did work overtime in violation of the policy although they were compensated appropriately and the work was “voluntary.”

More than half of Hon Hai’s sales come from Apple.

The Cupertino-based company launched its iPhone X on November 3. The device, which was met with heavy demand and reportedly plagued by manufacturing setbacks, arrived more than seven weeks after the launch of the iPhone 8 and iPhone 8 Plus.

According to the Financial Times (via Bloomberg), the students worked at the factory as part of a three-month “work experience” stint that was required to graduate. Half a dozen students told the publication they regularly worked 11-hour days building the iPhone X.

Having high school students working overtime to build a handset that was reportedly hampered by production delays certainly doesn’t look good. It’s even more concerning in the case of Apple as the company has grappled with overseas labor issues for years.

Li Qiang, founder of New York-based advocacy group China Labor Watch, tells Bloomberg that ultimately, it’s about production needs. Based on Apple’s actions, Qiang said, it seems like they don’t care about the labor standards they set previously.

Apple said it took prompt action when it found out about the matter.