Photo of Coldplay by Peter Ohs

It appears Coldplay's next album A Head Full Of Dreams may be coming Dec. 4.

As some ardent fans in London have discovered, a mysterious poster with imagery linked to the band was seen on the London Undergound, announcing a Dec. 4 date.

The geometric artwork matches what frontman Chris Martin sported on his shirt while performing at last month's Global Citizen Festival.

Anyone else spotted this mystery London Underground poster tonight? Yep, it's the new Coldplay album. December 4th. pic.twitter.com/Jk0ArzMhJu

— Lee Thompson (@leethommo) October 29, 2015

As we previously mentioned, Martin said he viewed the forthcoming LP as "the last Harry Potter book," noting that it's "not to say there won’t be another thing one day, but this is the completion of something ... I have to think of it as the final thing we're doing; otherwise, we wouldn't put everything into it."

A rep for Coldplay did not immediately provide comment.