BEIJING — Millions of Chinese women, and some men, woke on Aug. 13 to discover their spouse had, in effect, become their landlord.

On that day, the Supreme Court’s new interpretation of the 1980 Marriage Law came into force, stipulating that property bought before marriage, either outright or on mortgage, reverted to the buyer on divorce. Previously, the family home had been considered joint property. Experts agree the change would mostly affect women, since men traditionally provide the family home.

The result has been uproar — and, in the cities, a rush to add the wife’s name to title deeds.

Some husbands have agreed to this, but others have balked, and Chinese news outlets have already reported on marriage breakdowns caused by a husband’s refusal to add his wife’s name.

Marriage law experts and feminists are asking: Did China just take a great leap backward?

“Feudal society is back again. How many hundreds of years will it take before women are free again?” ran a typically angry post by a person called Jingmochengzhu on Sina Weibo, China’s biggest microblog, one of 1.4 million on the topic.