Chinese minors will be limited to one hour of online gaming every Friday, Saturday, and Sunday, a move meant to combat gaming addiction that was announced two days before the start of the new school year.

The new rule was published on Monday by the National Press and Publication Administration, which oversees media in China including news and cinema, state news agency Xinhua reported. “Online gaming addiction is a social problem,” an unnamed official told Xinhua.

The administration will only allow gaming companies to “provide services to minors for one hour from 8 p.m. to 9 p.m. on Fridays, Saturdays, Sundays, and legal holidays.” Any other time during the week will be off limits.

The restriction is the latest measure by authorities to tighten their control on online gaming, which various parts of the Chinese state have described as a threat to young people’s eyesight, education, and fitness.

The government requires game developers to verify users’ identities, and it had earlier limited online gaming hours for minors to between 8 a.m. and 10 p.m., a regulation for which last month tech giant Tencent announced a facial recognition system that would detect when children were playing after-hours.

Earlier this month, an article by state-run Economic Information Daily that called games “spiritual opium” for teenagers sent the stocks of Tencent and competitor NetEase plunging by between 10% and 15%, after which the article’s phrasing was adjusted.

Monday’s announcement was made after the stock market in Hong Kong, where both companies are listed, had already closed.