diff --git a/addons/delivery/stock.py b/addons/delivery/stock.py
index c9fd50986f7..23cc1563cff 100644
--- a/addons/delivery/stock.py
+++ b/addons/delivery/stock.py
@@ -160,13 +160,12 @@ class stock_move(osv.osv):
     _columns = {
         'weight': fields.function(_cal_move_weight, method=True, type='float', string='Weight', digits_compute= dp.get_precision('Stock Weight'), multi='_cal_move_weight',
                   store={
-                 'stock.move': (lambda self, cr, uid, ids, c={}: ids, ['product_id', 'product_qty', 'product_uom'], 20),
+                 'stock.move': (lambda self, cr, uid, ids, c=None: ids, ['product_id', 'product_qty', 'product_uom'], 20),
                  }),
         'weight_net': fields.function(_cal_move_weight, method=True, type='float', string='Net weight', digits_compute= dp.get_precision('Stock Weight'), multi='_cal_move_weight',
                   store={
-                 'stock.move': (lambda self, cr, uid, ids, c={}: ids, ['product_id', 'product_qty', 'product_uom'], 20),
+                 'stock.move': (lambda self, cr, uid, ids, c=None: ids, ['product_id', 'product_qty', 'product_uom'], 20),
                  }),
-                 
         }
 
 stock_move()
diff --git a/addons/purchase/stock.py b/addons/purchase/stock.py
index 987c76e372d..93cd142ac01 100644
--- a/addons/purchase/stock.py
+++ b/addons/purchase/stock.py
@@ -55,7 +55,7 @@ class stock_picking(osv.osv):
             ondelete='set null', select=True),
     }
     _defaults = {
-        'purchase_id': lambda *a: False,
+        'purchase_id': False,
     }
 
     def get_currency_id(self, cursor, user, picking):
diff --git a/addons/sale/stock.py b/addons/sale/stock.py
index 2855323c7a0..72e3f0a6c24 100644
--- a/addons/sale/stock.py
+++ b/addons/sale/stock.py
@@ -188,7 +188,7 @@ class stock_picking(osv.osv):
                     })
         return result
 
-    def action_cancel(self, cr, uid, ids, context={}):
+    def action_cancel(self, cr, uid, ids, context=None):
         res = super(stock_picking, self).action_cancel(cr, uid, ids, context=context)
         for pick in self.browse(cr, uid, ids, context):
             call_ship_end = True
diff --git a/addons/sale_margin/sale_margin.py b/addons/sale_margin/sale_margin.py
index 2f756d5ecda..3a0e09a0309 100644
--- a/addons/sale_margin/sale_margin.py
+++ b/addons/sale_margin/sale_margin.py
@@ -94,13 +94,13 @@ class account_invoice_line(osv.osv):
     _columns = {
         'cost_price': fields.float('Cost Price', digits=(16, 2)),
     }
-    def write(self, cr, uid, ids, vals, context={}):
+    def write(self, cr, uid, ids, vals, context=None):
         if vals.get('product_id', False):
             res = self.pool.get('product.product').read(cr, uid, [vals['product_id']], ['standard_price'])
             vals['cost_price'] = res[0]['standard_price']
         return super(account_invoice_line, self).write(cr, uid, ids, vals, context)
 
-    def create(self, cr, uid, vals, context={}):
+    def create(self, cr, uid, vals, context=None):
         if vals.get('product_id',False):
             res = self.pool.get('product.product').read(cr, uid, [vals['product_id']], ['standard_price'])
             vals['cost_price'] = res[0]['standard_price']
diff --git a/addons/stock_location/stock_location.py b/addons/stock_location/stock_location.py
index 01d3b906d29..1f6d7b78e61 100644
--- a/addons/stock_location/stock_location.py
+++ b/addons/stock_location/stock_location.py
@@ -52,10 +52,10 @@ class stock_location_path(osv.osv):
             ),
     }
     _defaults = {
-        'auto': lambda *arg: 'auto',
-        'delay': lambda *arg: 1,
-        'invoice_state': lambda *args: 'none',
-        'picking_type':lambda *args:'internal',
+        'auto': 'auto',
+        'delay': 1,
+        'invoice_state': 'none',
+        'picking_type': 'internal',
     }
 stock_location_path()