Mortgage rates surged to their highest level since September on Friday as bond yields moved higher due to the war in Iran.

The average rate on the 30-year fixed loan hit 6.41%, according to Mortgage News Daily. That is the highest rate since the first week of September, but still below the 6.78% notched at the same time last year.

Mortgage rates loosely follow the yield on the 10-year U.S. Treasury, which were up again Friday.

“This is counterintuitive for those who expect bonds to serve as a safe haven in times of uncertainty, but when war has a direct impact on inflation expectations, it’s more than enough to offset any of the safe haven benefit that might otherwise be seen,” wrote Matthew Graham, chief operating officer at Mortgage News Daily.

Even as rates began rising last week, mortgage demand from homebuyers rose, according to the Mortgage Bankers Association, but this week’s new surge could put a damper on the spring season, which is already plagued by other major headwinds.

Lennar, one of the nation’s largest homebuilders, reported disappointing first-quarter earnings. Its CEO, Stuart Miller, described headwinds for the broader market as including “high mortgage rates, constrained affordability, cautious consumer sentiment, and geopolitical uncertainty, especially now including the recent conflict in Iran.”

Just two weeks ago, rates had dropped to match a multiyear low, briefly touching 5.99%. Now, any savings from those lower rates is gone.

For someone buying a $400,000 home, around the national median, with 20% down on a 30-year fixed mortgage, the monthly payment is now about $115 more than it would have been two weeks ago.