diff --git a/addons/hr_timesheet_invoice/hr_timesheet_invoice.py b/addons/hr_timesheet_invoice/hr_timesheet_invoice.py
index 0c16fb4ffd4..1f795b6e97f 100644
--- a/addons/hr_timesheet_invoice/hr_timesheet_invoice.py
+++ b/addons/hr_timesheet_invoice/hr_timesheet_invoice.py
@@ -73,7 +73,7 @@ account_analytic_account()
 class account_analytic_line(osv.osv):
     _inherit = 'account.analytic.line'
     _columns = {
-        'invoice_id': fields.many2one('account.invoice', 'Invoice'),
+        'invoice_id': fields.many2one('account.invoice', 'Invoice', ondelete="set null"),
         'to_invoice': fields.many2one('hr_timesheet_invoice.factor', 'Invoicing'),
     }
 
diff --git a/addons/hr_timesheet_invoice/wizard/hr_timesheet_invoice_create.py b/addons/hr_timesheet_invoice/wizard/hr_timesheet_invoice_create.py
index 65ca5c31a07..7bc8583f676 100644
--- a/addons/hr_timesheet_invoice/wizard/hr_timesheet_invoice_create.py
+++ b/addons/hr_timesheet_invoice/wizard/hr_timesheet_invoice_create.py
@@ -36,6 +36,13 @@ class invoice_create(wizard.interface):
     def _get_accounts(self, cr, uid, data, context):
         if not len(data['ids']):
             return {}
+        #Checking whether the analytic line is invoiced or not
+        pool = pooler.get_pool(cr.dbname)
+        analytic_line_obj = pool.get('account.analytic.line').browse(cr, uid, data['ids'], context)
+        for obj_acc in analytic_line_obj:
+            if obj_acc.invoice_id and obj_acc.invoice_id.state !='cancel':
+                raise wizard.except_wizard(_('Warning'),_('The analytic entry "%s" is already invoiced!')%(obj_acc.name,))
+        
         cr.execute("SELECT distinct(account_id) from account_analytic_line where id IN (%s)"% (','.join(map(str,data['ids'])),))
         account_ids = cr.fetchall()
         return {'accounts': [x[0] for x in account_ids]}