Error with ConfigurationSerialization

I am trying to save and load Inventories from a config yml file. As you all know, Inventory is not ConfigurationSerializable, so I have to create a wrapper class. And what annoys me is every time I have to load it to the class, it gives me an InvalidConfigurationException: Could not deserialize object caused by YAMLException: Could not deserialize object caused by IllegalArgumentException: Class does not exist. I register it in onEnable() before I try to get the inventory, InventoryWrapper implements ConfigurationSerializable correctly and also contains a Map<String, Object> constructor, and nobody has tampered with the config. I just don't get it. MyStuff.java InventoryWrapper.java latest.log (several attempts with reloads)