In-N-Out Burger has filed a trademark infringement lawsuit against its rival Smashburger, claiming the Denver-based food chain’s new “Smashburger Triple Double” sounds too similar to its “Double Double” and “Triple Triple” burgers.

In a lawsuit filed Monday, Irvine, California-based In-N-Out Burger said Smashburger’s use of the “Triple Double” marks could mislead and confuse consumers into believing that In-N-Out has approved or licensed Smashburger’s products, reports the Orange County Register newspaper.

Irvine, California-based In-N-Out Burger, which founded 40 years ago, has held registered trademarks for its Double-Double since 1963 and the Triple Triple since 1966, according to the lawsuit.

Denver-based Smashburger was founded in 2007 and has 350 locations worldwide.

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