Tesla CEO Elon Musk joined a telephone conversation between President-elect Donald Trump and Ukrainian leader Volodymyr Zelensky, their first since the former got elected earlier this week.

Musk was one of Trump’s largest campaign donors, and his inclusion on Wednesday’s call illustrates the extent of his connection to the incoming president, possibly previewing the billionaire’s presence in the incoming administration. It’s unclear what role, if any, Musk could serve, though Trump has suggested he could oversee a government spending overview.