Table with BLOB value to json

I'm working with Flask, SQLALchemy and sqlite ... I have several tables which I can return completely in JSON format using:

enemies = enemyService.getAll()
return jsonify(json_list=[i.serialize for i in enemies])

Now, in this case the table contains an id, name and a BLOB which generates the following error:

UnicodeDecodeError: 'utf8' codec can not decode byte 0x8c in position 54: invalid start byte

How can I convert those BLOBs so that they can be "jsonizable"