Gold ETFs were testing their long-term support as bullion prices retreated Friday in response to a strengthening U.S. dollar.

The SPDR Gold Shares (NYSEArca: GLD) fell 0.5% Friday, with Comex gold futures down 0.8% to $1,257.4 per ounce, and was testing its long-term support at the 200-day simple moving average after breaking above the trend line in the previous session. GLD gained 4.4% over the past three months but remained 3.6% lower year-to-date.

Gold futures weakened from a six-month high Friday but was on pace to finish the week higher in response to safe-haven demand in a volatile equity market. However, gold investors’ attention were back on interest rates and the strength in the U.S. dollar.

“With the U.S. having very high real rates and gold offering no yield, the yellow metal falls in U.S. dollar terms,” Frank Holmes, chief executive and chief investment officer at U.S. Global Investors, told MarketWatch. Overall, however, he said he’s “very surprised that gold has held up so well with the strong U.S. dollar.”

The U.S. Global GO GOLD and Precious Metal Miners ETF (NYSEArca: GOAU) was also 2.3% lower Friday after jumping 7.3% over the past month.

Gold’s Relationship to U.S. Dollar

Gold typically exhibits an inverse relationship to the U.S. dollar. The Dollar Index (DXY), which tracks the USD’s moves against a basket of major international currencies, was up 0.7% Friday to 96.97.

“The metal has enjoyed a strong inverse relationship with the greenback throughout 2018, and the relationship is playing out today,” David Madden, market analyst at CMC Markets, said in a Friday research note.