Gold prices slumped to their lowest level of the year on Thursday, as a firmer dollar dulled the appeal of the yellow metal.

Comex gold futures hit their weakest level since Dec. 27 at $1,275.65 a troy ounce. It last traded at $1,277.45 by 8:40 AM ET (13:40 GMT), down $6.55, or around 0.5%.

Meanwhile, spot gold was trading at $1,278.64 per ounce, down $4.14, or almost 0.3%.

The U.S. dollar index, which measures the greenback’s strength against a basket of six major currencies, rose to 96.29, the best level since Jan. 3.

A stronger dollar can be a negative for commodities priced in the currency, making them more expensive to users of other currencies.