I've encountered a bug when using a binary field for storing a pdf, which I am not sure how to resolve.

Steps to reproduce:

1. Upload a file
2. Save
3. Use the edit button to upload another file over it
4. Save
5. Upload the edit button to upload again
6. Save and refresh the page
7. Observe

Expected result:

The third file is displayed/stored in the sale's order

Actual result:

The second file persists. Even deleting it, saving and then uploading a new file, still shows the second one on refresh.

Additional information
In my model, i've defined the field as follows

scanned_contract = fields.Binary(copy=False, help="Attach here the signed hard copy of the contract")​

Then, in my view I display it like this, using pdf_viewer widget:

xpath expr="//field[@name='signature']" position="after"
	​field widget="pdf_viewer" name="scanned_contract"/            
/xpath

Am I defining something wrong, or is this a bug with odoo/pdf_viewer itself?