With hotels in 87 countries, Marriott International Inc. is finding it harder to protect itself from currency swings as exchange rates in the $5.3-trillion-a-day market defy expectations.

The chain locked in its 2016 currency hedges about four months ago, anticipating the dollar would extend a three-year winning streak. Instead, the greenback has had a mixed performance, slumping against the euro and yen this year amid turmoil in global markets. That's a problem because the cost of the hedges would be wasted if the dollar weakens.

"For better or for worse, you are locking in," said Leeny Oberg, Marriott's chief financial officer, in a telephone interview from Bethesda, Md. The company set hedges in 2016 anticipating that the U.S. currency will strengthen, but less than last year.