The Washington, D.C.-based developer that just finished Fannie Mae’s headquarters is expanding north with a planned trophy office tower in Boston.

Carr Properties is partnering with National Real Estate Advisors in acquiring One Congress, the planned 1M SF, 43-story office tower at HYM Investment Group’s Bulfinch Crossing mixed-use development in downtown Boston. HYM will develop the tower, and the Carr-NREA JV will own it, the Washington Business Journal reports.

One Congress will be the only property in Carr’s portfolio outside Greater Washington. The company has developed millions of square feet of trophy office properties in recent years in D.C., Maryland and Virginia.

"[The Boston] market's on fire,” Carr Properties founder and CEO Oliver Carr III said at a Bisnow event in D.C. Wednesday. "We’re trying to go where our competition isn’t.”

The financial terms of the deal are unclear, as Carr is thought to have bought into the tower from NREA, which was already tied to One Congress, the Real Reporter reports. Details of Carr’s, NREA’s or HYM’s ownership stakes remain uncertain. HYM and NREA were already partners in developing the 2.9M SF Bulfinch Crossing, which is expected to include hotel, residential, retail and office components upon completion.

Construction at One Congress is expected to begin in summer 2019.