Directors of

Starbucks

(SBUX) - Get Report

authorized the repurchase of up to 10 million additional shares Thursday, expressing confidence in a stock that costs about 36 times next year's expected earnings.

The authorization, which doesn't guarantee the stock will be bought back, is in addition to 5.7 million shares outstanding under a previous program. Ten million Starbucks shares would cost about $520 million at the current price.

The company is coming off a typically strong month of same-store sales. Starbucks said Wednesday that April comps jumped 9% from a year ago, a little better than its standing 3% to 7% target.

"Starbucks business performance continues to generate strong cash flow, which enables us to execute further share buybacks, along with the ongoing investment in our growth strategy," the company said.

Starbucks' first share repurchase was set in September 2001. Since then, the company has bought back 27.2 million shares at a cost of $1 billion through Wednesday.

The shares added $1.63, or 3.2%, to $54.42 after hours Thursday.