Two U.S. watch companies—Genender International and Skagen Designs—have filed legal actions against each other over the design of Genender’s Hamlin watch line.

Skagen Designs’ suit alleges that Genender’s Hamlin watches illegally infringe on Skagen’s rights of trade dress under federal patent and trademark law. “Although we regret the need for litigation, it’s important that we take all necessary steps to protect our brand,” said Charlotte Jorst, co-owner of Skagen Designs with her husband, Henrik Jorst.

Genender International, of Wheeling, Ill., followed with a declaratory judgment lawsuit alleging that Skagen’s design patent is invalid because of “long-existing prior art.” The suit claims the watch designs in question aren’t protected under federal law, because they’re “not distinctive or unique” but have “long been used” by watch manufacturers. Genender seeks a court order that its Hamlin watches don’t infringe on any valid rights Skagen may have in its watch designs.

The two suits have been merged into a single case that will be heard in the U.S. District Court in Chicago.