[1.10.2] Save data to a world

I want to save as an example an integer to the world.

My problem is: I can save and load without a problem, but with a restart of the client i get a "null"

public class Test
{
private final static String nbt = "test";

@SubscribeEvent
public void test(PlayerInteractEvent.RightClickItem event)
{
	World world = event.getWorld();

	TestWorldSavedData data = new TestWorldSavedData(nbt);

	data.test = 10;

	world.getPerWorldStorage().setData(nbt, data);
}

@SubscribeEvent
public void test(PlayerInteractEvent.RightClickEmpty event)
{
	System.out.println(event.getWorld().getPerWorldStorage().getOrLoadData(TestWorldSavedData.class, nbt));
}

public static class TestWorldSavedData extends WorldSavedData
{
	public int test;

	public TestWorldSavedData(String name)
	{
		super(name);
	}

	@Override
	public void readFromNBT(NBTTagCompound tag) 
	{
		test= tag.getInteger(nbt);
	}

	@Override
	public NBTTagCompound writeToNBT(NBTTagCompound tag) 
	{
		tag.setInteger(nbt, test);
		return tag;
	}
}
}