Proterra has raised $155 million in a funding round co-led by Daimler and Tao Capital Partner, a deal that could transform the school bus market in North America.

Until now, Proterra has focused on producing electric buses for municipal, federal and commercial transit agencies. The company has developed a line of electric buses that can travel 350 miles on a single charge, enough range to last entire day. Proterra has sold hundreds of its all-electric buses as cities try to reduce tailpipe emissions.

This latest investment comes with a catch: Proterra will work with Daimler to possibly electrify the company’s Thomas Built Buses division, which manufactures a line of school buses. The two companies didn’t provide a lot of detail on when electric school buses might come to market.

For now, the two companies are only committing publicly to collaborating on an electric vehicle for the school bus market. Proterra, which has two factories in the U.S., will lend its battery and drive train expertise. Daimler will show Proterra how to scale its manufacturing business even further.

Proterra raised $140 million in January 2017. The company filed a restated certificate of Incorporation authorizing $100M in new equity funding on May 18, according to the Prime Unicorn Index.

G2VP and other technology investors also participated in this latest funding round, Proterra said.