Council officials have slapped "cancelled" stickers over posters that had been illegally put up around Luton.
Environmental health officers have put the bright yellow signs over music promoters' posters on lampposts.
Closer inspection revealed the poster reads: "Flyposting is an offence. This poster has been cancelled by Luton Borough Council."
But the word "cancelled" is in much larger letters, giving the impression that the event has been cancelled.
A spokeswoman for Luton council said: "Flyposting is unsightly and illegal. We will use all legal methods at our disposal to remove this blight from Luton."