Speculators lost money in last week’s oil price jump as they were forced to cover previous bets on falling prices, data from the New York Mercantile Exchange show.

Traders said many speculators had been betting on falling oil prices ahead of last week’s jump of $16.24 in less than 36 hours to a record $139.12 a barrel by Friday. Caught in a wrong bet, they had to buy back their positions on Monday.