Shares of Trivago (TRVG) were falling by 23% to $16.54 on heavy trading volume on Friday afternoon, after the hotel booking website company reported an unexpected second quarter loss, due to a rise in spending on marketing.

Trivago reported a loss of one cent per share, while analysts were expecting a breakeven quarter.

The company also lowered its outlook for 2018, leading Susquehanna to cut its price target on the stock to $21 from $23. The firm maintained its "neutral" rating on the stock due to concerns over its valuation.

"We continue to like Trivago, given its leadership position in the hotel metasearch space, large runway for growth and ability to [scale] margins over time," the firm said, according to Market Watch.

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