Doomsday is officially underway in London, and while the start of production on the upcoming Marvel movie is a big enough headline on its own, what’s even more eye-popping is Marvel Studios’ decision to let Robert Downey Jr.

Robert Downey Jr. has shared a new behind-the-scenes photo from the set of Avengers: Doomsday – and eagle-eyed fans have spotted a detail that might reveal something about his Doctor Doom costume.

Robert Downey Jr. shared a new photo from the set of Avengers: Doomsday and gave a nod to Hawkeye’s Jeremy Renner. Downey will return to the Marvel Cinematic Universe as Doctor Doom and made a post on social media as he films the new movie.