International Commission on Zoological Nomenclature
The grey-cheeked warbler was previously placed in the genus "Seicercus". A molecular phylogenetic study published in 2018 found that neither "Phylloscopus" nor "Seicercus" were monophyletic. In the subsequent reorganization the two genera were merged into "Phylloscopus" which has priority under the rules of the International Commission on Zoological Nomenclature.