Supreme Court Chief Justice John Roberts says the federal judiciary needs to do more to ensure judges don’t participate in cases where they have financial conflicts of interest.

Roberts made the comments as part of his annual report on the federal judiciary released Friday evening.

Roberts pointed to a series of stories recently in The Wall Street Journal that found that “between 2010 and 2018, 131 federal judges participated in a total of 685 matters involving companies in which they or their families owned shares of stock.” Federal judges and Supreme Court justices are required under a federal ethics law to recuse themselves from cases where they have a personal financial interest.

“Let me be crystal clear: the Judiciary takes this matter seriously. We expect judges to adhere to the highest standards, and those judges violated an ethics rule,” Roberts wrote in the nine-page report.

Roberts is one of three justices on the nine-member Supreme Court to hold individual stocks. Those holdings sometimes result in the justices recusing themselves from a case or selling stock in order to participate. The other justices who own individual stocks are Stephen Breyer and Samuel Alito. In the past those holdings have occasionally resulted in issues.