BGT Citygml not working in Cesium Ion

Hi, I’m trying to add this asset to Cesium Ion but I get this error during upload:

Error: Invalid File
File: bgt_pand.gml
Additional Information: Missing spatial reference system (srsName) and no source SRS given (--source-srs).

The file is a citygml file of the BGT. https://app.pdok.nl/lv/bgt/download-viewer/