One of the hottest investments on Wall Street is something of a surprise—it’s a battered long-dated Treasury bond fund.

Shares of the iShares 20+ Year Treasury Bond ETF are near a 16-year low and have lost more than half their value from their 2020 peak, but investors are piling in. They added more than $2 billion to the fund on Tuesday and Wednesday alone, bringing its total inflows for the year to $21 billion.