San Francisco on Thursday sued Oakland after officials there voted in favor of changing the name of the city’s airport to San Francisco Bay Oakland International Airport, saying the change will cause confusion and is already affecting its airport financially.

Last week, the Board of Commissioners for the Port of Oakland voted unanimously to move forward with the name-change and scheduled a second vote for final approval on May 9. The airport is currently called Oakland International Airport.

“We had hoped Oakland would come to its senses, but their refusal to collaborate on an acceptable alternative name leaves us no choice but to file a lawsuit to protect SFO’s trademark,” San Francisco City Attorney David Chiu said in a statement.