Upwork shares fell sharply after the freelance marketplace cut its full-year guidance, overshadowing a second-quarter earnings beat and reviving concerns that AI is eroding the work it brokers.

The stock dropped as much as 21% in after-hours trading on Monday and closed on Tuesday down about 15% at $8.39.

The company reported second-quarter revenue of $191.7m, down 2% year on year but ahead of expectations, with adjusted EBITDA up 12% to $64.1m and non-GAAP earnings of $0.41 a share.

It was the guidance that unsettled investors. Upwork cut its full-year revenue forecast from a range of $760m-$790m to $730m-$750m, and guided third-quarter revenue to $176m-$184m, below a consensus near $194m.

Two figures underneath the results explain the caution. Gross services volume, the total value of work transacted on the platform, fell to $966.4m, down around 4%. Active clients fell 4% to 763,000.