Stocks and bonds are again moving in tandem after diverging in recent months—a sign some investors may be losing faith in the so-called reflation trade.

The Dow Jones Industrial Average has soared more than 1,000 points so far this year and closed at a record of 20821.76 Friday. Bond prices, too, are rising, driving down the yield on the benchmark 10-year Treasury note to 2.317% Friday, the lowest since late November, from 2.446% at the end of 2016. Yields fall as bond prices rise.

It is a shift from late last year when investors were selling bonds and buying stocks, anticipating that large fiscal stimulus from President Donald Trump would lead to accelerated growth and higher inflation, a bet known as the reflation trade.

The new pattern is generating debate among investors.

Some money managers and traders believe that a rising Treasury bond market, often seen as a haven for investors, is a warning that valuations of riskier assets—such as stocks, corporate bonds and emerging-market assets—may be stretched. The Dow closed at a record for an 11th consecutive session Friday, the longest such streak since 1987.