Downtown Boston’s growing tech reputation just got a 160K SF boost.

Software company Klaviyo signed a lease for nearly a third of the 475K SF 125 Summer St. office building in downtown Boston, building owner Oxford Properties Group announced Wednesday. The Boston-based email marketing platform will become the building’s largest tenant.

“We could not be more excited to expand our global headquarters right here in the heart of Boston at 125 Summer St.,” Klaviyo Chief Revenue Officer Steve Wietrecki said in a statement. “This is our city, it’s our home and Klaviyo is committed to building the next pillar technology company right here in the center of everything. With this location, we can vastly expand our workforce and make a positive impact on the greater Boston community for years to come.”

Klaviyo’s new office comes after several years of growth at another Oxford building. The software company first signed a 25K SF lease in the fall of 2016 at 225 Franklin St. and had plans to grow to 75K SF. The company’s growth trajectory had it recently in the market looking to expand by 135K SF, so the landlord and tenant pivoted to 125 Summer St.

Klaviyo will occupy the fifth through 11th floors. Other tenants at 125 Summer St. include Asics, Haemonetics, Analog Devices and Tatte Bakery & Café.