Volkswagen and Tesla may be bitter rivals on the electric vehicle market. But their CEOs are great admirers of each other.

This week, after a four-year-old Volkswagen scandal came back to haunt its CEO Herbert Diess, his friend at Tesla, Elon Musk, stood up without hesitation and shouted support from an ocean away.

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On Tuesday afternoon, in response to a Bloomberg Opinion article ridiculing Diess’ role in Volkswagen’s high-profile Dieselgate scandal of 2015, Elon Musk tweeted, “Herbert Diess is doing more than any big carmaker to go electric. The good of the world should come first. For what it’s worth, he has my support.”

Herbert Diess is doing more than any big carmaker to go electric. The good of the world should come first. For what it’s worth, he has my support. — Elon Musk (@elonmusk) September 24, 2019

Here’s a bit of background information about the Dieselgate scandal: In September 2015, the U.S. Environmental Protection Agency (EPA) found that Volkswagen had intentionally manipulated emission controls in its cars during lab testing, which resulted in misleading lab reports that understated those cars’ actual greenhouse gas emission level by up to 40 times. The misconduct affected about 11 million Volkswagen cars made between 2009 and 2015 worldwide, including half a million cars in the U.S.

Volkswagen was ordered to pay $2.8 billion in criminal fines and $1.5 billion in civil damages in the U.S.

The scandal came back into the spotlight last month when a German court found that Volkswagen had deployed a cheat device in a software update that was designed to “fix” emission numbers in the cars affected by the Dieselgate.

Tying into the renewed controversy around Volkswagen, the Bloomberg article on Tuesday called attention to the unfortunate timing of Diess joining the German auto giant shortly before the scandal erupted. (Per his job offer, Diess was supposed to start at Volkswagen on October 1, 2015, but he offered to start early on July 1. The scandal was exposed in September.)

Also this week, Diess faced fresh charges in Germany relating to Dieselgate. German prosecutors alleged that Diess had intentionally withheld knowledge about the scandal from shareholders before Volkswagen shares plummeted by a third in September on the news.

Volkswagen argued that those accusations were groundless, as the company didn’t anticipate the financial consequences of the EPA’s probe into its misconduct.