Stitch Fix, a personal shopping service, initially saw its stock tick up on the earnings beat before plunging 20% to $35.02 a share, its lowest price in more than a month.

The company reported revenue of $318.3 million in its fiscal fourth quarter ended July 28, an increase of 23% from the same quarter a year ago. Analysts had been expecting revenue of $318.6 million. Stitch Fix also said active clients rose 25% to 2.7 million, which was below a forecast of 2.81 million clients from StreetAccount.

While the revenue was slightly below expectations, Stitch Fix indicated revenue in the current quarter could be below analyst forecasts. Stitch Fix sees revenue in its fiscal first quarter coming in between $354 million and $360 million. Analysts had been expecting revenue at the top end of that range, at $359 million.

The selloff reflects what appears to be less of a sense of disappointment over Stitch Fix’s most recent quarter and more of a growing sense of caution about the startup’s ability to compete against Amazon. Last month, Amazon began testing Scout, a personalized shopping recommendation service that is currently focused on home design. Scout could easily expand into fashion, which would offer Stitch Fix a formidable competitor.

Stitch Fix was one of a handful of tech startups that went public late last year, paving the way for a strong year in 2018 for tech IPOs. Stitch Fix’s stock rallied as high as $51.19 a share in September, representing a 240% gain over its offering price, before the news about Amazon Scout caused the stock to tumble.

In a statement, Stitch Fix CEO Katrina Lake described the quarter as “another strong quarter for us” and announced the company is expanding into the U.K. market. “We believe our ability to create a uniquely personalized shopping experience is something that will resonate with consumers and brands outside of the U.S.,” Lake said.