WATCH: Crap extra ruins trailer for Christopher Nolan's war epic 'Dunkirk'

Oops.

The subject matter for Christopher Nolan's forthcoming war epic is no laughing matter. It tells the dramatic real-life story of the Dunkirk evacuations during World War II, and more specifically Operation Dynamo, a 1940 mission that freed over 300,000 Allied troops trapped on all sides by the Nazis.

Befitting of such sombre material, the teaser trailer for the movie is suitably brutal and moving. It conveys the devastating and often futile nature of war quite beautifully. Many will be reassured that a story that still echoes with the relatives and loved ones of those involved is in safe hands with Nolan.

That said, a few eagle-eyed viewers have noticed that an extra featuring in the minute-long trailer probably shouldn't make the final cut for the cinema release in July 2017. Whilst everyone else is completely lost in the moment and doing a sterling job, the chap in question is smirking like an idiot.

Not only that but whilst all his fellow actors are shielding themselves from air attack, he seems to be taken by surprise during his daydreaming and reacts with almost casual slackness. As you can see below, he's caused quite a stir...

Dunkirk Trailer - Best Extra Fail Ever https://t.co/NsGw31sqIe — THE SIGHTING (@SAlienxandre) August 6, 2016

I can't watch the Dunkirk trailer without looking at that same extra every time. You know the one. pic.twitter.com/xmsZNdQlkD — Sasha's Harry Movie Chat (@StylesMovieNews) August 6, 2016

now my eyes gravitate to that not so "in the moment" extra in the Dunkirk teaser every single time. — MKSongbird (@MKSongbird) August 7, 2016

that extra in the Dunkirk teaser has really irritated me — lily 🍒 (@finelinelily) August 6, 2016

Stop saying the #Dunkirk teaser is amazing. Nothing happens in it except for a really bad extra being a really bad extra. — Greg Warne (@GrumpyGrog) August 5, 2016

This article originally appeared on JOE.co.uk.