June 18, 2021—An electric vehicle maker filed a legal challenge this week against the U.S. Postal Service's contract to rebuild its fleet, Reuters reports.

USPS in February awarded the 10-year and up to $6 billion contract to Wisconsin-based Oshkosh Defense to manufacture as many as 165,000 next generation postal vehicles, a mix of internal combustion and battery-powered vehicles.

On Wednesday, EV-maker Workhorse Group filed a legal challenge to the contract in the U.S. Court of Federal Claims, Reuters reports. Workhorse had proposed to build USPS an all-electric fleet and had support in Congress.

Earlier this summer, Ohio lawmakers raised concerns about the proportion of electric vehicles included in the contract. As it stands, just 10 percent of the new USPS fleet is slated to be electric.