Allbirds said Tuesday that its third-quarter revenue rose 33% from last year, while its losses widened as the cost of opening stores and listing its stock weighed on its results.

Allbirds shares fell around 6% in extended trading on the report, which was its first as a public company. While its sales climbed significantly, investors didn’t like to see continued losses.

For the three months ended Sept. 30, net losses widened to $13.8 million, or 25 cents per share, from a loss of $7 million, or 13 cents a share, a year earlier.

Sales climbed 33% to $62.7 million from $47.2 million a year ago. The sustainable shoemaker said its revenue was up 40% on a two-year basis.

Co-founder and CEO Joey Zwillinger said the company saw notable strength in its stores in the United States. Shoppers also responded well to product launches, including a recently debuted performance apparel line.

Allbirds has been expanding its assortment of goods beyond the wool sneakers that it is best known for. It now sells a variety of footwear, including running sneakers, trail shoes and high-tops. The company has said it will continue to add more apparel items to the mix, hoping to lure in new customers to the Allbirds brand and convince existing customers to spend more money on new items.

Allbirds is also investing in store growth to try to boost profitable sales. Its business has grown primarily online since its inception. Roughly 89% of its revenue came from e-commerce last year. But that comes with transportation costs, higher return rates and other expenses.

The company ended the quarter with 31 retail locations, including those outside the U.S. Allbirds has previously said it’s only “scratched the surface” with its brick-and-mortar footprint.

All of these investments come at a cost, however, which is part of the reason why Allbirds is still losing money.

Allbirds’ selling, general and administrative expenses were $33.0 million, or 52.6% of revenue compared with 42.5% of revenue for the same period in 2020. Costs related with four new store openings and hiring more employees contributed to the uptick, it said.

For fiscal 2021, Allbirds said net revenue should be up anywhere between 23% and 24% from year-ago levels, amounting to between $270 million and $272 million.

Allbirds shares are down slightly since the company went public on Nov. 3. The stock closed Tuesday at $19.24, about 9% below its opening trade price of $21.21.

Find the full earnings press release from Allbirds here.