The Securities and Exchange Commission Chairman Gary Gensler said a full ban of the controversial payment for order flow (PFOF) practice is “on the table,” financial newspaper Barron’s reported on Monday, citing an interview.

SEC staff is reviewing the practice and could come out with proposals in the coming months, the report here said.

Gensler has in the past been critical of the PFOF practice, whereby wholesale market makers pay broker-dealers to send them client orders that they execute on their own trading platform or a third-party platform. He has said the practice raises several conflict-of-interest questions.

The SEC did not immediately respond to a Reuters request for comment on Monday.

Shares of app-based retail brokerage Robinhood Markets, which relied on PFOF for more than three-quarters of its revenue in the first quarter, closed down 6.9 percent. at $43.64.