Being an automaker that exclusively produces all-electric vehicles, Tesla has been gaining significant revenue over the years by selling federal greenhouse gas credits to fellow carmakers, which are needed by the car companies to offset the sales of internal combustion vehicles in the US market. Filings earlier this year have revealed that two of Tesla’s most notable credit buyers are none other than General Motors Co. (GM) and Fiat Chrysler Automobiles NV (FCA).

In filings to the state of Delaware, GM and FCA disclosed that they have an agreement to purchase greenhouse gas credits from Tesla. These filings, while light on details, are nevertheless notable, as they confirm that even established, veteran carmakers such as GM and Fiat Chrysler are looking to Tesla as a means to comply with the United States’ environmental regulations.

FCA’s purchase of credits from Tesla is quite unsurprising considering that the company has already been revealed to have entered an estimated $500 million open pool deal with the Silicon Valley-based electric car maker for the European region, which would allow Fiat Chrysler to count Tesla’s vehicles as part of its fleet to avoid incurring emissions penalties. What was surprising about the Delaware filings was that GM was purchasing credits from Tesla as well.

GM, after all, has been producing the Chevy Volt plug-in hybrid and Chevy Bolt EV for the US market for years. Despite the recent retirement of the Volt, it was largely assumed that GM’s electric and electrified vehicle lineup would leave the automaker in the clear when it comes to regulatory compliance. Nevertheless, Mike Taylor, founder and president of Houston-based environmental credit consultant and broker Emission Advisors, noted that GM’s decision to purchase credits from Tesla could be part of the company’s preparations for the future, especially if political tides shift in the 2020 election. “This might not be a bad hedge. If a Democrat gets elected in 2020, GM may need the credits and prices may go up,” Taylor said.

This assumption appears to have been highlighted by GM spokesman Pat Morrissey. In a statement to Bloomberg, the spokesman noted that the credits GM bought from Tesla are insurance against “future regulatory uncertainties.” FCA spokesman Eric Mayne, for his part, indicated that US standards are getting stricter at a pace that “far exceeds” the current level of demand for electric cars that are required for compliance. “Until demand catches up with regulatory requirements, and there is regulatory relief, we will use credits as appropriate,” Mayne stated.

Tesla has not issued a comment about GM and FCA’s credit purchases so far, though it should be noted that Chief Financial Officer Zachary Kirkhorn pointed out during a call with prospective investors that sales of credits will be a more significant part of the electric car maker’s business in the following years. The previous quarters have proven lucrative for Tesla in this light, as the company reported $216 million in revenue from the sale of regulatory credits in the first quarter alone.

Automakers in the United States appear to be dependent on credits to meet the country’s regulations so far. For the 2017 model year, for example, all American automakers were found to have complied with US rules, though the EPA has noted that most large car companies used credits to meet the requirements.

