The developer of Adblock Plus is annoyed because iOS 9 has its own ad-blocking feature, so that's what's up.
In iOS 9, Apple is opening the door for extensions that "block cookies, images, resources, pop-ups, and other content," which is good news for users but bad news for publishers and advertisers.
It's also a bit of a blow to existing popular ad blockers, who might now be pushed out the picture - particularly Adblock Plus, which lets certain adverts pay to pass through the software's filter.
Adblock Plus is about to roll out an iPhone browser, which may become redundant before it even gets off the ground.
I'm a business, man
Ad blocking is a morally dubious activity in an era where publishers need adverts in order to offer free content to readers, but the developer of Adblock Plus is clearly a tad cheesed off with Apple nonetheless.
"So far very little is known about Content Blocking Extensions, available in Safari 9 and iOS 9," said Sebastian Noack. "We appreciate and support Apple's attempts to finally catch up on extensions, but those latest changes will create either the best possible landscape for Safari extensions, or the worst - especially for Adblock Plus."
He added: "We are nervously awaiting how powerful their block lists will be".