It's been a difficult few days for Treasurys.
This may be a bit surprising, given that the stock market has been down for four-straight sessions, and bonds' safe-haven status means they often enjoy a boost when stocks fall.
But some market professionals say that with the Federal Reserve's next move becoming increasingly uncertain, the traditional relationship between stocks and bonds is breaking apart.
"This might be an early hint of a different future regime," said Laeeth Isharc, partner at advisory firm Kaleidic Associates. "Growth has disappointed recently … but investors should be cautious about thinking [Fed Chair Janet] Yellen is a dove. She is driven by data and models, and if the labor market continues to improve, she will tighten policy even if that hurts equities."
Given that bond prices could consequently fall due to Fed tightening while stocks fall alongside them, "we should be aware of the possibility of a breakdown of the correlation between stocks and bonds," Isharc wrote to CNBC.