Supreme Court Justice Ruth Bader Ginsburg participates in a discussion during the Library of Congress National Book Festival at the Walter E. Washington Convention Center on Saturday, August 31, 2019.

Supreme Court Justice Ruth Bader Ginsburg is not attending arguments in the Supreme Court on Wednesday, because of an illness.

Chief Justice John Roberts said at the start of arguments that Ginsburg was "indisposed due to illness." A court spokeswoman said that she was at home due to a stomach bug.

The Supreme Court on Wednesday heard two arguments on Wednesday, including a $20 billion racial discrimination case against cable giant Comcast, which owns CNBC parent NBCUniversal. Ginsburg will participate in the cases based on transcripts of oral arguments.

Ginsburg had a perfect attendance record for 25 years until she underwent surgery for cancer last December.

Earlier this year, Ginsburg, a four-time cancer survivor, was undergoing treatment for what likely was pancreatic cancer, according to a statement from the Supreme Court, which said in August that she was treated for a "tumor on her pancreas."

Ginsburg had previously been treated for colon and pancreatic cancer, as well as for cancerous growths on her lungs.

She's been active since completing radiation treatment on Aug. 23, attending various public events across the nation. After the latest treatment, Ginsburg said she was excited to get back to the bench.

"I can safely predict that the new term will have a fair share of closely watched cases, and I look forward to the challenges ahead," she said, speaking at a student event at the Georgetown University Law Center.

At 86, Ginsburg is the oldest justice and is considered the leader of the Supreme Court's liberal wing, which is outnumbered by the conservative wing 5-4. She was appointed by Democratic President Bill Clinton in 1993.