Could Cesium retain images even if the WMTS server provide the empty tiles?

Hi all,

I have a problem about the function of WMTS provider. When I try to create a new image layer through WMTS provider, it can present the proper images to the earth. But if I still zoom in the range until the display level is exceeded the maximum value and WMTS server provides the empty tiles, the canvas would stop to display the WMTS layer and the base map would be shown. The popular GIS software, like ArcGIS and QGIS, would still display the most precise level images coming form WMTS even if the WMTS server don’t transfer any tiles. Could Cesium also retain to display the latest level tiles and improve the displaying effects? Thanks a lot~