The PowerShares DB U.S. Dollar Index Bullish Fund (NYSEArca: UUP) returned more than 3% last year, making it one of 2016’s best-performing developed markets currency exchange traded funds. With 2017 still fresh, some traders are concerned the benchmark dollar ETF has rallied too far too fast.

Expectations that the Federal Reserve will boost interest rates multiple times this year are prompting some investors to speculate the dollar has more upside ahead of it.

UUP tracks the price movement of the U.S. dollar against a basket of currencies, including the euro, Japanese yen, British pound, Canadian dollar, Swedish krona and Swiss franc. A higher interest rate typically supports the U.S. dollar since the currency becomes more attractive to foreign-seeking investors and diminishes the supply of money sloshing around in the markets. Importantly, UUP could still offer investors significant upside even after its recent sharp rally.

“After a big rate rally, sliding bond yields have recently put pressure on the dollar, and Gordon expects this trend to continue. From a technical standpoint, the trader believes that an intraday chart of the dollar-tracking ETF signals that the dollar rally has run its course,” according to CNBC.

Expectations that the U.S. President-elect Donald Trump would help U.S. economic growth with stimulus measures also supported the rise in the dollar.

“Trump’s success, in other words, depends on what the dollar does. And right now, it’s freakishly strong, having risen 25% against its major trade partners’ currencies since mid-2014,” reports Quartz.

The yen is another one of the major developed market currencies currently showing weakness against the greenback. The euro is another must watch currency for dollar bulls.

While the ECB’s efforts to weaken the euro this year have not delivered on par with investors’ expectations, some market observers still believe the currency is heading for more downside. That does not mean the euro does not face more near-term downside, a scenario that could worsen for the common currency if the dollar rises in anticipation of higher interest rates in the U.S. After raising interest rates earlier this month, the Federal Reserve is expected to raise rates three times in 2017.

Euro weakness would benefit the ProShares UltraShort Euro (NYSEArca: EUO). Underscoring the euro’s prominence on the global currency stage and investors’ willingness to bet on weakness for the currency, EUO is one of the largest currency ETFs trading in the U.S. Another idea for euro bears to consider is the VanEck Vectors Double Short Euro ETN (NYSEArca: DRR).

For more information on the USD, visit our U.S. dollar category.