The rivalry between Tesla and Amazon continues in the wake of Jeff Bezos’ announcement about his Blue Origin’s first lunar lander, Blue Moon. Upon the release the spacecraft, Elon Musk was quick to chime in with his thoughts about the announcement.

Musk tweeted to Bezos, “Oh stop teasing, Jeff,” complete with a winking smiley face. This was accompanied by an altered picture of the spacecraft, with a tongue-in-cheek reference that reads, “Blue Balls” on it instead of “Blue Moon” as the spacecraft is actually called.

Musk and Bezos have had a fierce competition with their space projects. Musk has SpaceX under his leadership, and Bezos is running with his Blue Origin company. Both companies are aiming to be the first to launch satellites into space to provide internet to areas that are without access.

This is not the first time that Musk has thrown some shade at Bezos for his work with Blue Origin as he called Bezos a “copycat” in another tweet last month when Blue Origin announced its Project Kuiper.