Authorities in China have come up with a novel way of detecting illegal lending: note who’s commonly suing others for not paying back loans.

The Higher People’s Court in Eastern China’s Jiangsu province said that lenders who have been plaintiffs in five or more such cases in the province within a year will be put on a watch list. Such high volume implies they may be running a lending business, which requires a license.

China has been cracking down on illegal lending, which often involves punitively high interest rates, as part of a broader effort to rein in the country’s shadow banking sector, a key driver of financial risk.

If those on the list are confirmed to be operating an illegal business, the lending contracts involved in the case will be annulled, and the borrowers will have to pay back only the principal plus a base interest rate, the statement said.

The list will not be released to the public, the court said, but will be shared with local public prosecutors, public security bureaus, and financial regulators.

Related: 'Missiles' Are Shooting Trouble Into China’s Underground Lending Market