JSON Decoder can't decode bytes object in Python 3.x

Error occured by tutorial sample using SQLAlchemy and SQLite in Python 3.2.3.

CRITICAL/MainProcess] Can't decode message body: TypeError('initial_value must be str or None, not bytes',) (type:'application/json' encoding:'utf-8' raw:'b\'{"retries": 0, "task": "mytask.add", "errbacks": null, "callbacks": null, "kwargs": {}, "eta": null, "args": [3, 2], "id": "cf0ba54b-ed2e-49b6-ba1b-8b2c6477fc11", "expires": null, "utc": true}\' (192b)'')