Africa has the fastest-growing continental economy on the planet. And the thing that has been growing fastest of all is debt—personal, corporate and government. In 2015 Africa and its boosters will start to worry that the debt boom is getting out of hand.

Sovereign bonds issued by some of the world’s most far-out “frontier” economies, often denominated in local currencies, are snapped up by hungry investors from Omaha to Zurich. In 2014 countries like Senegal, Côte d’Ivoire (less than five years after a government-debt default) and Zambia placed bonds worth as much as $1 billion, with all the issues oversubscribed. Kenya’s record-breaking sale of $2 billion in debt was oversubscribed four times over.

These government borrowings are in essence massive bets that the African growth story will continue. More betting will follow before the party finally ends—even Ghana, already deep in debt and with the continent’s worst-performing currency, had no difficulty raising another $1 billion in euro-denominated debt in late 2014. The African borrowing binge, which began in 2007 and has been driven by investors’ hunger for yield in the post-crisis economy, looks likely to carry on until interest rates and investment returns in the rest of the world start to normalise.