U.S. mortgage rates rose for the first time since early March.

The average for a 30-year, fixed loan was 6.39%, up from 6.27% last week, Freddie Mac said in a statement Thursday. The increase was the first since March 9.

Buyers are encountering a housing market where affordability has been squeezed by high prices and a surge in borrowing costs over the past year. 

Inventory is also constrained because many owners are staying put, opting to stick with mortgages that often have lower rates than lenders currently offer. Sales of previously owned homes dropped by more than forecast in March, according to data released Thursday by the National Association of Realtors.

“Home prices have stabilized somewhat, but with supply tight and rates stuck above 6%, affordable housing continues to be a serious issue for many potential homebuyers,” Sam Khater, Freddie Mac’s chief economist, said. “Unless rates drop into the mid-5% range, demand will only modestly recover.”

Newer homes are faring better, with homebuilders benefiting from the limited supply of properties for sale. Buyers have also flocked to newer houses in part because of the discounts and rate buy-downs offered by the companies. 

On Thursday, builder D.R. Horton Inc. reported better-than-expected quarterly orders in what Chairman Donald Horton called an “encouraging start” to the spring selling season.

This article was provided by Bloomberg News.