Parsing of GLTF json string not working

[oligraphics]

var storage = new SimpleStorage(); context.ParseJson(json, storage); context.Load();
Throws "Value cannot be null."
This works though:
var path = Application.dataPath + "/temp.gltf";File.WriteAllText(path, json); context.Load(path);
Using the exact same GLTF json string.

What's up here?