NEW YORK, United States — Retailer Gap said Thursday that its sales slumped in February, sending its shares lower in after-hours trading.

Gap said its total revenue fell 1 percent to $918 million, and sales at stores open at least one year fell 4 percent. Analysts had expected those sales to grow 1.4 percent, according to Thomson Reuters.

Sales at stores open at least one year are considered an important measurement of retailer performance because they leave out results from stores that opened or closed within the last year, focusing on stores that have remained in operation.

Shares of Gap Inc. slid 83 cents, or 2 percent, to $40.60 in extended trading. The stock is down 1.6 percent in the year to date.

Old Navy, Gap's largest brand, performed the best over the four weeks that ended on Sunday. The San Francisco-based company said revenue from Old Navy stores open at least a year was unchanged compared to 2014. Sales at Gap stores slipped 7 percent and Banana Republic revenue declined 5 percent.