diff --git a/addons/account/invoice.py b/addons/account/invoice.py
index 9ae8a141f97..3f675f90a07 100644
--- a/addons/account/invoice.py
+++ b/addons/account/invoice.py
@@ -385,7 +385,7 @@ class account_invoice(osv.osv):
                 raise orm.except_orm(_('Configuration Error!'),
                      _('There is no Accounting Journal of type Sale/Purchase defined!'))
             else:
-                raise orm.except_orm(_('UnknownError'), str(e))
+                raise orm.except_orm(_('Unknown Error'), str(e))
 
     def confirm_paid(self, cr, uid, ids, context=None):
         self.write(cr, uid, ids, {'state':'paid'}, context=context)