In Texas federal court, Tesla (TSLA.O) filed a lawsuit against Cap-XX on Friday, alleging that the Australian company’s supercapacitors used to store energy in electric vehicle batteries violate two US patents held by a Tesla subsidiary.

Elon Musk, the CEO of Tesla, swore in 2014 not to “initiate patent lawsuits against anyone who, in good faith, wants to use our technology.” The firm claims that the legal action is in reaction to a claim of patent infringement brought by Cap-XX against Tesla subsidiary Maxwell Technologies in 2019.

The lawsuit stated that Tesla was bringing the action against Cap-XX to defend its intellectual property rights since Maxwell had a history of invention that led to the creation of its own patents, which are now under Tesla’s ownership.