Illness has forced Vandenberg's MoonKings to cancel.
The band were due to appear on the Main Stage this Sunday at the event.
They said in a statement:
"Unfortunately Vandenbergs MoonKings won't be able to make it to Planet Rockstock this Sunday, as our singer Jan Hoving is prohibited from traveling abroad due to avian flu. Besides being MoonKings singer, Jan has his own poultry farm.
"We're terribly sorry, as the band was really looking forward to playing this festival, and we regret this message and the short notice."
The rest of the event will still continue as planned, and we'll bring you any further information about this development as soon as we can.
For all the information about Planet Rockstock and to get tickets, head to planetrock.com/rockstock.