Tesla CEO Elon Musk sniped at Silicon Valley neighbor Apple twice during a conference call to discuss Tesla earnings on Monday.

Although the companies don’t compete directly today, Apple is reportedly building an electric self-driving vehicle under a project code-named Titan, and has attracted a number of engineers and executives away from Tesla. The Titan project is reportedly run by Doug Field, who returned to Apple in 2018 after five years at Tesla.

When asked about Tesla’s supply chain, Musk said that there’s a misperception that Tesla uses a lot of cobalt, a key material in the production of lithium-ion cells used in both smartphones and electric cars.

“Apple uses I think almost 100% cobalt in their batteries and cell phones and laptops, but Tesla uses no cobalt in the iron-phosphate packs, and almost none in the nickel-based chemistries,” Musk said. “On on a weighted-average basis we might use 2% cobalt compared to say, Apple’s 100% cobalt. Anyway, so it’s just really not a factor.”

Some cobalt mined in places like the Democratic Republic of the Congo has been linked to human rights abuses such as child labor. In 2019, Apple, in addition to Tesla and other major technology companies, was named as defendants in a human rights lawsuit, according to The Guardian.

In a conflict minerals report published earlier this year, Apple said it publishes a list of all conflict minerals and cobalt smelters and refiners, and all of Apple’s cobalt suppliers participated in audits in 2020. An Apple representative didn’t return a request for comment.

Later in the call, Musk made a crack about Apple’s so-called “walled garden,” which is named because Apple strictly controls what software can be installed on the iPhone through its App Store. Apple’s walled garden is facing scrutiny from lawmakers and other companies, including in an antitrust trial that took place earlier this year after it was sued by Epic Games over App Store fees and policies.

“I think we do want to emphasize that our goal is to support the advent of sustainable energy,” Musk said in response to a question about letting competitors use its charger network. “It is not to create a walled garden and use that to bludgeon our competitors which is used by some companies.”

Musk then faked a cough and said, “Apple.”

During the call, Musk said he likely would not appear on future Tesla earnings calls unless he has “something really important” that he needs to say.