General Motors’ much-trumpeted technology bets haven’t worked out well lately. Ironically, that is one reason it can afford to score an easy goal with investors.

A so-called accelerated share repurchase worth $10 billion is big for a company that had a market value of just $40 billion before the announcement. Some $6.8 billion of stock—about 17% of the total—will be canceled immediately, with the rest following over the next year. Mechanically, that should increase analysts’ forecasts for GM’s earnings per share next year by roughly 20%. The stock rose about 10% Wednesday morning.