Updated from 9:33 a.m.

Costco

(COST) - Get Report

posted a 21% increase in first-quarter profits that was in line with expectations, but traders only saw downside as the company fell slightly short on the revennue side.

The largest U.S. warehouse club said it earned $193.2 million, or 40 cents a share, for the quarter ended Nov. 21, up from $160.2 million, or 34 cents a share, for the year-ago period. Despite the gain, the discounter's shares were recently down $1.13, or 2.1%, to $47.77.

Its total sales rose 10% to $11.34 billion, while same-store sales, or those at warehouses open at least year, rose 7%. Wall Street was looking for total sales of $11.5 billion, according to consensus estimates from Thomson First Call.

The company said its sales gains were reduced by the implementation of an Emerging Issues Task Force Issue that mostly affected its vendor coupon and rebate programs. Without the change, its sales would have gained 11% with same-store sales up 8%.

In addition to its online operations, Costco runs 449 warehouses in the United States, Puerto Rico, Canada, the U.K., Korea, Taiwan, Japan and Mexico.