The bourses will also bar trading in foreign companies and stapled securities via the Hong Kong stock link, according to a statement by the Shanghai Stock Exchange on Saturday, which said many investors don’t understand the risks associated with new products. Xiaomi tumbled as much as 9.6% before paring declines to 1.9% at the close.

The move comes before the three classes of shares are included in the city’s Hang Seng Composite Index in the third quarter, which would otherwise have made them eligible for the stock connect.

Hong Kong opened the door for companies with weighted-voting rights in April, with rules designed to lure Chinese tech firms. The new regulations allowed the type of structure favoured by founder-led tech companies, which enable leaders to keep control even after going public. Dual-class shares, as they’re commonly known, were previously banned in the city, and aren’t permitted in China’s stock market.

“Companies like Xiaomi are well known in China and might attract big flows from the mainland – regulators certainly don’t want such big outflows to cross the border while the A-share market remains weak,” said Banny Lam, head of research at CEB International Investment Corp. “Such potentially big outflows would pressure its currency and hurt liquidity conditions.”