Gov. Charlie Baker wants to sell a permanent easement to a small part of the historic property that hosts the Massachusetts State House, a move that will allow developers to build an extension to multi-million dollar condos on an adjacent property. 

The request was included in a supplementary budget the governor filed with the Legislature late last week, according to a Boston Globe report.

If the easement moves forward, developers hope to build an extension to 25 Beacon St., a six-story, 28,494-square-foot mansion. That construction would include three “au pair” suites and a superintendent's living quarters in the basement.

It’s not clear how big the parcel will be: the report cites unnamed state officials who told the paper it might be as large as 300 square feet, but others said the land in question is actually smaller.

The au pair units will be offered with six condos that are priced between about $9 million to $11 million, according to the report.

At least one official expressed surprise to the paper, noting the first they heard of the proposal was through a phone call from their reporter.

“You don’t give away a permanent easement, no matter how small, to public land that has such historic significance as John Hancock’s pasture land, to a private developer,’’ Galvin said. “Why should we the public give up historic public land just to make more money for a developer?” 

A spokesperson for the governor told the paper that the construction will be "tiny." 

The requested easement will "simply enlarge four existing 5-foot windows on a building that abuts the State House and will not damage or change the appearance of our State Capitol grounds in any way,” she said.