No one is loving the rapid rise of Roku’s stock more than short-seller Andrew Left.

Although known more for making bets that a company’s stock price will fall, Citron Research’s Left made the rare call of venturing a bullish bet on Roku in May.

And the move has paid off.

While the size of Left’s investment is unknown, Roku’s stock has surged 59 percent since Left closed his short position and announced he went long on May 25.

On Thursday alone, the stock soared 21 percent, to an all-time high of $57.32, after the streaming giant reported late Wednesday that active accounts increased 46 percent over the last year.

“We are excited by the momentum that is building to make our TV streaming ecosystem the best in the industry,” Roku Chief Executive Anthony Wood said in a letter to shareholders Wednesday.

In May, Left wrote, “The move to cutting the cord and [over-the-top] advertising is real and it is a megatrend that Citron not only does not want to be short, but at this valuation I want to be long … What a difference six months makes.”