Rivian Automotive shares soared Wednesday, a day after the electric vehicle manufacturer expanded its partnership with Volkswagen in a move aimed at helping both firms find ways to grab more of the market for EVs.

Shares of Rivian jumped over 15% after the EV maker announced a $5.8 billion investment from German automaker Volkswagen as part of their joint venture.

The new agreement, which builds on an earlier announcement, calls for the German automaker to invest $5.8 billion in Rivian, a maker of electric vehicles.