Chinese authorities have stepped up their crackdown on organized illegal gambling that makes use of WeChat’s “red envelope” feature, the country’s supreme court said Tuesday.

WeChat first introduced the immensely popular feature in 2014. Unlike regular money transfers on WeChat, red envelopes allow users to hide the amount being transferred until the recipient completes the transfer. Chat group members may also send red envelopes that can be opened by multiple people, each of whom receives a different, randomized amount.

Inviting gamblers into WeChat groups, and setting up gambling games involving red envelopes for profit under certain conditions could qualify as “opening a casino” under China’s criminal law, said the Supreme People's Court, China’s highest court.

Under Chinese law, people caught opening casinos can face fines and up to ten years of imprisonment.