In a Twitter message Monday, Daimler trolled Musk over how much it is investing in electric cars. The tweet included a link to Daimler’s electrification goals.

Daimler’s provocation was in response to Musk’s own tweet sent over the weekend that expressed disappointment in the German automaker’s announcement it was going to invest $1 billion into its Alabama factory to produce an electric SUV there.

Daimler announced Sept. 21 that it plans to produce a Mercedes electric SUV under a new brand called EQ at the Tuscaloosa, Ala. factory. The automaker is also building a separate battery plant next to the factory. The EQ brand will cover a number of electric products, from vehicles and charging services to home energy storage units.

Here’s Daimler’s tweet:

You're absolutely right @elonmusk. Here the missing zero: Investing >$10bn in nxt gen EVs & >$1bn in battery prod. 👉 https://t.co/Tk747isWAc

— Daimler Truck (@DaimlerTruck) September 25, 2017

And here’s Musk’s tweeted that started the whole interaction:

That's not a lot of money for a giant like Daimler/Mercedes. Wish they'd do more. Off by a zero.

— Elon Musk (@elonmusk) September 24, 2017

Musk responded to Daimler within hours of the tweet with one word: “good.”