draw2d reader does not render standard element

I have a json file, which looks like so:

[{"type":"draw2d.shape.layout.FlexGridLayout","id":"6ce58ff3-5cca-36ca-7b68-bb9544cb8389","x":215,"y":78,"width":120,"height":80,"alpha":1,"angle":0,"userData":{},"cssClass":"draw2d_shape_layout_FlexGridLayout","ports":[{"type":"draw2d.HybridPort","id":"84d1c387-38fe-2a25-84fb-bcc1803b3238","width":10,"height":10,"alpha":1,"angle":0,"userData":{},"cssClass":"draw2d_HybridPort","bgColor":"#4F6870","color":"#1B1B1B","stroke":1,"dasharray":null,"maxFanOut":9007199254740991,"name":"hybrid0","port":"draw2d.HybridPort","locator":"draw2d.layout.locator.InputPortLocator"},{"type":"draw2d.HybridPort","id":"ac5e1ebc-27f3-b7dd-95b6-a3c7cbfd0a95","width":10,"height":10,"alpha":1,"angle":0,"userData":{},"cssClass":"draw2d_HybridPort","bgColor":"#4F6870","color":"#1B1B1B","stroke":1,"dasharray":null,"maxFanOut":9007199254740991,"name":"hybrid1","port":"draw2d.HybridPort","locator":"draw2d.layout.locator.OutputPortLocator"},{"type":"draw2d.HybridPort","id":"c33ae6cc-3ab2-a565-6bcb-37a4a55c9483","width":10,"height":10,"alpha":1,"angle":0,"userData":{},"cssClass":"draw2d_HybridPort","bgColor":"#4F6870","color":"#1B1B1B","stroke":1,"dasharray":null,"maxFanOut":9007199254740991,"name":"hybrid2","port":"draw2d.HybridPort","locator":"draw2d.layout.locator.TopLocator"},{"type":"draw2d.HybridPort","id":"9d3e21fb-3424-48d8-0d5d-327cdfe1c537","width":10,"height":10,"alpha":1,"angle":0,"userData":{},"cssClass":"draw2d_HybridPort","bgColor":"#4F6870","color":"#1B1B1B","stroke":1,"dasharray":null,"maxFanOut":9007199254740991,"name":"hybrid3","port":"draw2d.HybridPort","locator":"draw2d.layout.locator.BottomLocator"}],"bgColor":"#FFFFFF","color":"#DBDBDB","stroke":2,"radius":0,"dasharray":null}]

So, it's just a normal json representation, provided by draw2d.io.json.Writer (I mean that I did not make this json by hand, this json was generated by draw2d.io.json.Writer).

However, when I do

var reader = new draw2d.io.json.Reader();
reader.unmarshal(canvas, json);

I get nothing on my canvas. What is wrong with that and how can I fix it?