Gold traders are paying the most in at least half a decade to maintain their bullish bets.

The cost of rolling futures into a later-dated contract was recently the highest in about six years, said Bernard Sin, head of currency and metal trading at Geneva-based refiner MKS (Switzerland) SA. Those holding June futures would have paid an extra $3.40 an ounce on May 23 to swap that position for the most-active August contract, Comex data show.

Speculators have to roll contracts forward before they expire to avoid having to take physical delivery. While money managers cut their net-long position by a quarter in the latest week, their wager is still 76 percent bigger than the average in the past five years, U.S. government data show. Gold reached a 15-month high on May 2 on expectations that the Federal Reserve wouldn’t raise interest rates as fast as previously thought.

“The bullish sentiment is coming at a cost for gold longs,” Brad Yates, head of trading for Dallas-based Elemetal LLC, one of the biggest U.S. refiners, said last week. “There’s massive speculative position starting to roll, so they’re selling June and buying August.”

On Wednesday, the August contract was $2.80 more expensive than June futures, up from $2.10 a month earlier, Comex data compiled by Bloomberg show. The biggest spread between the August and June contracts for delivery in 2015 only reached $2 and was at 40 cents this time last year. On May 23, August surpassed June as the contract with the biggest open interest.

Year’s Advance

While gold retreated about 7 percent since May 2 as traders increased bets that the Fed will raise rates by next month, prices are still up 15 percent in 2016. That’s the best start to a year in a decade.

Each Comex contract rises in price through February. In some markets, traders take advantage of the structure, known as contango, by buying a commodity and selling at a future date to profit from the difference after paying costs such as storage.

“The fact that the spread is moving higher could be a reflection of the underlying bullishness in the market,” Georgette Boele, an analyst at ABN Amro Group NV in Amsterdam, said by e-mail. “Contango is often a reflection of inventory dynamics, but also in gold’s case, expectation of higher prices further down the road.”