With the Avengers: Age of Ultron press tour in full swing, Mark Ruffalo has finally revealed why he hasn’t done a Hulk movie with Marvel.

We’ve had Thor, Iron Man and Captain America stand-alone movies, but the rest of the Avengers team (Black Widow, Hawkeye and the Hulk) have yet to receive the solo treatment.

Speaking to Collider while promoting Avengers: Age of Ultron, Mark Ruffalo finally explains the simple reason Marvel hasn’t — and can’t — make a movie starring Bruce Banner’s lumpy alter-ego.

“Marvel doesn’t really have the rights to that yet,” Ruffalo reveals. “That’s still Universal’s property, so there’s that issue. That’s a big impediment to moving forward with that. Now I don’t think that’s insurmountable, by the way, but I don’t know where it’s going from here for me.”

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What Ruffalo is saying is that although Universal still retains the rights from their 2008 version The Incredible Hulk (starring Ed Norton), it’s surely only a matter of time before Marvel wrangles the property for themselves.

But considering that Marvel’s schedule is pretty much locked down until 2020, an eventual Hulk movie might not be starring Mark Ruffalo.

However, don’t abandon hope yet; Ruffalo also notes that he’s contractually bound to appear in four more Marvel movies after Age of Ultron, “and that could always go further.”

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As of right now, the Hulk is still not slated to appear in Captain America: Civil War, which is basically Avengers 2.5 considering that Cap will be joined by Iron Man, the Black Widow and Hawkeye.

Although chances are slim for a Hulk cameo, “Sometimes these things happen at the last minute in this world,” Ruffalo allows. “I really don’t know where I fit in from here on out, and I’m not sure they do.”

Would you like to see Mark Ruffalo star in a solo Hulk movie?

Avengers: Age of Ultron premieres May 1, 2015.