Error on images when copying a product

When copying a product that have images, this error occur :

Constraint Error
A product can have only one image with the same name
Traceback (most recent call last):
  File "/home/arthur/Projets/openerp/7.0/ocb-server/openerp/netsvc.py", line 292, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/arthur/Projets/openerp/7.0/ocb-server/openerp/service/web_services.py", line 626, in dispatch
    res = fn(db, uid, *params)
  File "/home/arthur/Projets/openerp/7.0/ocb-server/openerp/osv/osv.py", line 189, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/home/arthur/Projets/openerp/7.0/ocb-server/openerp/osv/osv.py", line 153, in wrapper
    tr(osv_pool._sql_error[key], 'sql_constraint') or inst[0])
  File "/home/arthur/Projets/openerp/7.0/ocb-server/openerp/netsvc.py", line 71, in abort_response
    raise openerp.osv.osv.except_osv(description, details)
except_osv: ('Constraint Error', 'A product can have only one image with the same name')