diff --git a/addons/resource/resource.py b/addons/resource/resource.py
index d3bc6313419..21552e73d52 100644
--- a/addons/resource/resource.py
+++ b/addons/resource/resource.py
@@ -188,7 +188,7 @@ class resource_calendar(osv.osv):
     def get_weekdays(self, cr, uid, id, default_weekdays=None, context=None):
         """ Return the list of weekdays that contain at least one working interval.
         If no id is given (no calendar), return default weekdays. """
-        if id is None:
+        if not id:
             return default_weekdays if default_weekdays is not None else [0, 1, 2, 3, 4]
         calendar = self.browse(cr, uid, id, context=None)
         weekdays = set()
@@ -338,7 +338,7 @@ class resource_calendar(osv.osv):
         work_dt = start_dt.replace(hour=0, minute=0, second=0)
 
         # no calendar: try to use the default_interval, then return directly
-        if id is None:
+        if not id:
             working_interval = []
             if default_interval:
                 working_interval = (start_dt.replace(hour=default_interval[0], minute=0, second=0),
@@ -462,7 +462,7 @@ class resource_calendar(osv.osv):
 
             working_intervals = self.get_working_intervals_of_day(cr, uid, id, **call_args)
 
-            if id is None and not working_intervals:  # no calendar -> consider working 8 hours
+            if not id and not working_intervals:  # no calendar -> consider working 8 hours
                 remaining_hours -= 8.0
             elif working_intervals:
                 if backwards:
@@ -556,7 +556,7 @@ class resource_calendar(osv.osv):
                 compute_leaves=compute_leaves, resource_id=resource_id,
                 default_interval=default_interval,
                 context=context)
-            if id is None or working_intervals:  # no calendar -> no working hours, but day is considered as worked
+            if not id or working_intervals:  # no calendar -> no working hours, but day is considered as worked
                 planned_days += 1
                 intervals += working_intervals
             # get next day
diff --git a/openerp/addons/base/tests/test_views.py b/openerp/addons/base/tests/test_views.py
index 1cb04f75fe2..50d2818cd21 100644
--- a/openerp/addons/base/tests/test_views.py
+++ b/openerp/addons/base/tests/test_views.py
@@ -9,6 +9,7 @@ from lxml.builder import E
 
 from psycopg2 import IntegrityError
 
+from openerp.osv.orm import modifiers_tests
 from openerp.exceptions import ValidationError
 from openerp.tests import common
 import openerp.tools
@@ -857,6 +858,10 @@ class test_views(ViewCase):
                 string="Replacement title", version="7.0"
             ))
 
+    def test_modifiers(self):
+        # implemeted elsewhere...
+        modifiers_tests()
+
 class ViewModeField(ViewCase):
     """
     This should probably, eventually, be folded back into other test case
diff --git a/openerp/osv/orm.py b/openerp/osv/orm.py
index 835e29da7f9..be5c69d9a01 100644
--- a/openerp/osv/orm.py
+++ b/openerp/osv/orm.py
@@ -118,13 +118,13 @@ def test_modifiers(what, expected):
         node = etree.fromstring(what)
         transfer_node_to_modifiers(node, modifiers)
         simplify_modifiers(modifiers)
-        json = simplejson.dumps(modifiers)
-        assert json == expected, "%s != %s" % (json, expected)
+        dumped = simplejson.dumps(modifiers)
+        assert dumped == expected, "%s != %s" % (dumped, expected)
     elif isinstance(what, dict):
         transfer_field_to_modifiers(what, modifiers)
         simplify_modifiers(modifiers)
-        json = simplejson.dumps(modifiers)
-        assert json == expected, "%s != %s" % (json, expected)
+        dumped = simplejson.dumps(modifiers)
+        assert dumped == expected, "%s != %s" % (dumped, expected)
 
 
 # To use this test: