A proposed Polish ban on certain Ukrainian nationalist symbols is causing a rift between Ukraine and Poland, one of Kyiv’s closest relationships in its war against Russia.

On Monday, Polish President Karol Nawrocki proposed a law banning “Bandera symbols,” referring to the controversial Ukrainian nationalist leader Stepan Bandera. He argued that the move would benefit Polish-Ukrainian relations as it would disprove “Russian propaganda,” but the proposal already sparked outrage in Ukraine.