Some of the most widely used types of gold bars would be subject to U.S. tariffs, customs agency officials ruled, a particular blow to Switzerland’s large gold refining industry.

The price of U.S. gold futures spiked Friday, a day after Switzerland was hit with 39% American tariffs on its goods, including 1-kilogram gold bullion bars.

The U.S. has unexpectedly slapped tariffs on imports of some gold bars, according to the Financial Times, roiling the market for the precious metal. Why is this disruptive? The global gold market uses futures traded on metals-trading exchange Comex to hedge its positions.