The Sherlocks have admitted photoshopping the Y Not line-up poster so they appear higher than The Amazons.
In the original, released by Y Not Festival, The Sherlocks feature on the fourth tier of acts. But in the one they shared they're in the third tier.
"We just thought we'd do it for a bit of a laugh. Now everyone's talking about it," drummer Brandon tells Newsbeat.
A spokesperson for Y Not says there is only one official poster.
The Sherlocks' Twitter feed had shown a line-up where they were moved up the order - but that post has since been deleted.
Better-known bands headlining festivals are usually placed higher in a line-up poster.
The band run their own Twitter feed, and Brandon says he couldn't believe the reaction when they put out the altered poster today.
"It's pretty scary how things can blow up. All the lads were saying that. Just from one picture," said the 24-year-old.
Some fans on social media guessed the band were behind the joke.
Congrats on another milestone achieved on your way to the top..at this rate you’ll be photo shopping your way onto the main stage at Glastonbury.— Liam K (@KaviK21) February 7, 2018
Brandon wouldn't tell us which of the band has the Photoshop skills, but they have since worked their magic - as that fan suggested - on the Glastonbury poster.
Other fans have responded by getting a bit handy with Photoshop themselves.
Y Not festival is no stranger to being in the news - last year it was cancelled halfway through the weekend.
Heavy rain caused the ground to turn to mud and the organisers deemed it too unsafe to continue.
The Sherlocks were due to play a secret set, but as well as headliners The Vaccines, they weren't able to perform.
Brandon says they're looking forward to coming back this year.
"Every time we've played, we've rammed every tent out, and this time we're on the main stage. It's one of our favourite festivals."
In January a new location was announced, adjacent to where it took place last year.
The festival will take place between July 27 and 29.