Share of Robinhood Markets Inc fell by nearly 7% on Monday following a news that PayPal Holdings Inc may start an online brokerage service. Reports have also emerged saying, regulators were looking at imposing a potential ban on a practice that accounts for the bulk of the company’s revenue.

Shares of Robinhood extended an early decline after CNBC’s report that PayPal was exploring ways to let U.S. customers trade individual stocks on its platform.

Shares of the popular gateway for trading meme stocks tumbled further after the SEC’s chairman Gary Gensler told Barron’s in an interview published on Monday that payment for order flow has “an inherent conflict of interest.”

Retail brokers such as Robinhood send their customers’ orders to wholesale brokers rather than exchanges in the controversial practice known by the acronym PFOF.

“That may not be the most efficient markets for the 2020s,” said Gensler to Barron’s in the interview.

Gensler did not say whether the SEC had found instances where conflicts of interest had harmed investors.

The SEC is scrutinizing PFOF over concerns it may incentivize brokers to send customer orders to trading platforms that maximize their own profit instead of providing customers the best execution for their trades.

Robinhood’s simple user interface has been popular with investors trading from home during the coronavirus-induced COVID-19 pandemic.

A spokesperson for Robinhood said, as stated earlier by its chief financial officer, the company would defend its customers and ensure it does not put up barriers that keep people out.