Getting empty xnonce1 when calling mining.subscribe from p2pool

[alttalker1]

I am sending the following message to p2pool:

Code:

{"id":1,"method":"mining.subscribe","params":["myclient/0.1"]}

And I am getting back:

Code:

{"error": null, "jsonrpc": "2.0", "id": 1, "result": [["mining.notify", "ae6812eb4cd7735a302a8a9dd95cf71f"], "", 4]} 

Note how the xnonce1 is returned as empty string, while xnonce2_size is 4, which is Ok.

Why is it empty? What am I missing