The strike authorization vote passed with an 85% margin, the union said. Investors didn’t seem concerned, however. Costco stock was up 1% to $952.28 in midmorning trading Tuesda

The unionized Costco workers are on a contract that expires Jan. 31, according to their Teamsters representatives.

Members of the Teamsters union have authorized a strike against Costco on February 1 unless they reach a deal with the warehouse retailer before the current contract expires 31.