We report two new analogs of the N871b fluorogen that contain CycloOctaTetraene. We have studied the photostability of fluorescent complexes of the FAST protein with new compounds by confocal microscopy when staining living HeLa Kyoto cells. One of the new analogs exhibits a higher photostability in the complex with FAST than the previously published N871b fluorogen. The results indicate that cyclooctatetraene is a highly promising compound for the modification of dyes based on arylidene imidazolones.