A Trump administration ruling that gold bars will be subject to tariffs stunned traders who had assumed they would be exempted, throwing bullion markets into turmoil.

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.

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.