Shares of Peloton spiked more than 11% on Wednesday after Greenlight Capital’s David Einhorn said shares of the company are significantly undervalued, CNBC has learned. 

Einhorn made the pitch to investors while he was riding a Peloton bike, a person familiar with his remarks said. It was not immediately clear what Einhorn believed Peloton shares should trade at.

Over the summer, Greenlight Capital, the hedge fund that Einhorn founded in 1996, disclosed it had a $6.8 million stake in the company as of June 30. 

Peloton’s stock tends to be volatile and is up a little more than 1% so far this year, as of Tuesday’s close. 

Einhorn’s comments come one day after the company announced that it was partnering with Costco to sell its Bike+ in the retailer’s stores and online as it looks to reach younger, wealthier consumers with the discretionary income to buy pricey exercise equipment. 

The company is currently being led by two board members after CEO Barry McCarthy stepped down earlier in this year. It’s in the process of finding a new CEO and expects to announce its next top executive this year.

When reporting earnings in August, Peloton indicated that it was ready to focus more on profitability over growth after completing a massive refinancing that pushed out its debt maturities and bought it some time to affect a turnaround. 

Peloton didn’t immediately return a request for comment from CNBC.