China’s vow to encourage the nation’s leading companies to list in Hong Kong is helping spur a rare surge in the $5 trillion stock market, but dealmakers aren’t ready to turn optimistic.

The Hang Seng Index jumped about 9% last week for its best gain since 2011 after China’s securities regulator said on April 19 that it will support initial public offerings in Hong Kong. Bourse operator Hong Kong Exchanges & Clearing was among the biggest winners, rallying 17%.

While a number of factors drove the index’s gains, including bullish analyst calls on China and inflows by mainland investors seeking a hedge against a weakening yuan, the regulator’s comments sent a signal that the city could expect more favorable policies to strengthen its position as a finance hub.