Roku’s shares plunged nearly 22% in after-hours trading Wednesday after the company issued a forecast losses for the coming quarter.

The maker of streaming TV devices predicted first-quarter revenue of $120-$130 million, falling short of the $131.7 million estimate of analysts surveyed by Thomson Reuters. It also forecast a loss of $15 to $21 million in the coming quarter — citing the impact of an accounting rule change governing when customer revenue can be recognized.

“We do anticipate that the new revenue recognition standards will add quarterly variability based on the size and timing of signing of new agreements with content partners and Roku-powered licensees,” Chief Executive Anthony Wood said in a letter to shareholders.

That wasn’t exactly music to investors’ ears. Roku’s stock plummeted to $39.90 in after-market trading, a loss of $11.20 from the day’s closing price of $51.50.

Roku had been the beneficiary of mighty investor enthusiasm, which sent the company’s stock soaring well above its $14 initial public stock offering price last September. The company was seen as poised to capitalize on the growing popularity of online streaming.

The company said it saw a “fantastic” holiday quarter, with revenue of $188.3 million topping analysts’ estimates of $182.5 million and net income of $6.9 million, or 6 cents per share. Roku said the number of active accounts grew to 19.3 million as the company added consumers who purchased its stand-alone streaming devices or connected via televisions that licensed its streaming technology.