Costco (COST) revealed weaker-than-expected fourth-quarter sales on Thursday as robust demand in August could not wholly offset slowness recorded earlier in the summer.

The Issaquah, Wash.-based wholesale giant reported sales of $31.8 billion, up 1% from $31.5 billion a year ago, missing average analyst estimates of $33.1 billion.

However, sales at stores open longer than a year, a key growth metric known as same-store sales, grew by 5%, helping to send shares of Costco up about 1.3% to $113 in pre-market trade.

For the four weeks ended Sept. 1, Costco said sales increased by 7% year-over-year to $7.44 billion, though the company in July posted a disappointing 4% rise in monthly sales that helped to offset some of the late-quarter gains. 

The wholesaler will release full quarterly results on Oct. 9.

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