Chick-fil-A says it will no longer adhere to its pledge of serving antibiotic-free chicken.

In a statement released Monday, the fast-food company said that starting this spring it would serve chicken that was free only of antibiotics ‘important to human medicine,’ or those commonly used to treat people.

It said its poultry going forward may have been raised with animal antibiotics, though ‘only if the animal and those around it were to become sick.’ The chicken will continue to be free of artificial preservatives, steroids and added hormones, it said.

Chick-fil-A first announced its no-antibiotics pledge in 2014.

But amid an avian-flu outbreak that devastated poultry supplies nationwide, chicken farmers who’d previously sought to avoid antibiotics have been forced to turn to them. Last July, food processing giant Tyson announced it was ending its ‘no antibiotics ever’ pledge. Poultry producer Perdue Farms still has its pledge in place, while rival Pilgrim’s Pride says it uses some.

While world health officials have long raised concerns about the potential of any antibiotics in food to degrade the human body’s immunity to disease treatments, the Food and Drug Administration has said it is more concerned about the use of antibiotics commonly prescribed to humans than ones used to treat animal illnesses.