Tom Hanks warned his son Truman Hanks to take his acting role seriously in their new movie A Man Called Otto.

In the comedy-drama, the Forrest Gump star plays Otto Anderson, the grumpiest man in America, whose attempts to end his own life are constantly thwarted by his boisterous new neighbours.

Although his 26-year-old son Truman isn’t an actor, he agreed to play a younger version of Otto, and before the shoot began, Hanks warned his son that he needed to treat the job as professionally as any other performer.

“Truman plays my character’s younger self, but he’s not the actor in the family – he’s an artist and is going to be a cinematographer. We talked about it a lot and it was all his choice, but I said to him, ‘No matter what your last name is, you are going to have to hit the marks,'” he recalled on The Graham Norton Show. “Not everyone is cut out for that, but he did a magnificent job and I thought he was extraordinary.”

In acting, “hitting your mark” means landing on the exact spot, or mark, to deliver your lines as the camera, lighting, and sound equipment have all been set up for that specific position.

The Oscar-winning star – who has four children – admitted he doesn’t know if Truman will continue acting after A Man Called Otto.

“It’s still to be discovered if he’s caught the acting bug – we will see where he wants to go with it,” he shared. “I’ve always said to the kids, ‘It’s great work if you can get it but you’ve got to make it stick.’ But his passion is shaping the shot rather than being in the shot.”

His appearance on The Graham Norton Show airs in the U.K. on Friday.

A Man Called Otto will be released in the U.S. on 30 December.

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