Millennium Tower’s reign as Boston’s priciest condo development may be short-lived, as the developer of the new Four Seasons Hotel and Private Residences in Back Bay said he has scored the city’s most expensive sale.

Carpenter & Co. CEO Richard Friedman announced Thursday he had a $40M deal for a unit in the new One Dalton tower, the Boston Globe reports. The previous record holder was John Grayken's $35M grand penthouse at Downtown Crossing's Millennium Tower, purchased last year. The 61-story Four Seasons development will be the city’s tallest residential building when it opens next year.

The average price of a condo in Boston has risen 68% in the last six years, and luxury units are the driving factor. Just last year, the average price for a unit in a full-service building was $2M. Sales at the new Four Seasons have started at close to $2.5M, and it is not guaranteed the $40M sale will even wind up being the priciest unit in the building.