KFC filed a lawsuit against Church’s Texas Chicken for infringing its trademark rights by using the term “original recipe” in advertising.

The lawsuit, filed last week in federal court in Texas, alleges fast-food rival Church’s “suddenly” began using the branding to promote its fried chicken in September. Advertisements on television, social media and the Church’s website state “Our Original Recipe is back” along with photos of their line of fried chicken.

KFC said it sent a letter to Church’s in October objecting to the use of the phrase, but it was ignored.

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KFC has used the trademark phrase “original recipe” for over half a century. In the lawsuit, the company said it continues to be a cornerstone of KFC’s advertising to promote its fried chicken made with “a secret blend of 11 herbs and spices that result in a unique, signature flavor.”

“That combination of 11 herbs and spices is one of the most well-known, iconic trade secrets in the food industry. And it is that combination of ingredients that KFC promoted with the original recipe trademark,” the lawsuit states.

KFC told the United States District Court for the Eastern District of Texas that Church’s continued use of the trademark phrase in its advertisements is likely to confuse consumers and negatively impact its brand.