diff --git a/addons/account/account.py b/addons/account/account.py
index 0c32aea78f5..2bae5c5c7e4 100644
--- a/addons/account/account.py
+++ b/addons/account/account.py
@@ -2303,8 +2303,7 @@ class account_model(osv.osv):
         pt_obj = self.pool.get('account.payment.term')
         period_obj = self.pool.get('account.period')
 
-        if context is None:
-            context = {}
+        context = dict(context or {})
 
         if data.get('date', False):
             context = dict(context)
diff --git a/addons/account/account_move_line.py b/addons/account/account_move_line.py
index 84778dc0928..143c8ff5468 100644
--- a/addons/account/account_move_line.py
+++ b/addons/account/account_move_line.py
@@ -674,8 +674,7 @@ class account_move_line(osv.osv):
 
     #TODO: ONCHANGE_ACCOUNT_ID: set account_tax_id
     def onchange_currency(self, cr, uid, ids, account_id, amount, currency_id, date=False, journal=False, context=None):
-        if context is None:
-            context = {}
+        context = dict(context or {})
         account_obj = self.pool.get('account.account')
         journal_obj = self.pool.get('account.journal')
         currency_obj = self.pool.get('res.currency')
@@ -1090,8 +1089,7 @@ class account_move_line(osv.osv):
         return r_id
 
     def view_header_get(self, cr, user, view_id, view_type, context=None):
-        if context is None:
-            context = {}
+        context = dict(context or {})
         context = self.convert_to_period(cr, user, context=context)
         if context.get('account_id', False):
             cr.execute('SELECT code FROM account_account WHERE id = %s', (context['account_id'], ))
diff --git a/addons/account/wizard/account_report_general_ledger.py b/addons/account/wizard/account_report_general_ledger.py
index cd242e79657..f15f65a6de4 100644
--- a/addons/account/wizard/account_report_general_ledger.py
+++ b/addons/account/wizard/account_report_general_ledger.py
@@ -49,8 +49,7 @@ class account_report_general_ledger(osv.osv_memory):
         return res
 
     def _print_report(self, cr, uid, ids, data, context=None):
-        if context is None:
-            context = {}
+        context = dict(context or {})
         data = self.pre_print_report(cr, uid, ids, data, context=context)
         data['form'].update(self.read(cr, uid, ids, ['landscape',  'initial_balance', 'amount_currency', 'sortby'])[0])
         if not data['form']['fiscalyear_id']:# GTK client problem onchange does not consider in save record
diff --git a/addons/document/document.py b/addons/document/document.py
index a30099df905..244cde2d7b2 100644
--- a/addons/document/document.py
+++ b/addons/document/document.py
@@ -620,9 +620,8 @@ class node_context(object):
     def __init__(self, cr, uid, context=None):
         self.dbname = cr.dbname
         self.uid = uid
+        context = dict(context or {})
         self.context = context
-        if context is None:
-            context = {}
         context['uid'] = uid
         self._dirobj = openerp.registry(cr.dbname).get('document.directory')
         self.node_file_class = node_file
diff --git a/addons/l10n_be/wizard/l10n_be_partner_vat_listing.py b/addons/l10n_be/wizard/l10n_be_partner_vat_listing.py
index 8fa11545dee..b692966bb4f 100644
--- a/addons/l10n_be/wizard/l10n_be_partner_vat_listing.py
+++ b/addons/l10n_be/wizard/l10n_be_partner_vat_listing.py
@@ -45,6 +45,7 @@ class partner_vat(osv.osv_memory):
     _name = "partner.vat"
 
     def get_partner(self, cr, uid, ids, context=None):
+        context = dict(context or {})
         obj_period = self.pool.get('account.period')
         obj_partner = self.pool.get('res.partner')
         obj_vat_lclient = self.pool.get('vat.listing.clients')
diff --git a/addons/point_of_sale/point_of_sale.py b/addons/point_of_sale/point_of_sale.py
index b4476a9505e..47e1c7895d0 100644
--- a/addons/point_of_sale/point_of_sale.py
+++ b/addons/point_of_sale/point_of_sale.py
@@ -443,8 +443,7 @@ class pos_session(osv.osv):
         """
         call the Point Of Sale interface and set the pos.session to 'opened' (in progress)
         """
-        if context is None:
-            context = dict()
+        context = dict(context or {})
 
         if isinstance(ids, (int, long)):
             ids = [ids]
@@ -537,8 +536,7 @@ class pos_session(osv.osv):
         return True
 
     def open_frontend_cb(self, cr, uid, ids, context=None):
-        if not context:
-            context = {}
+        context = dict(context or {})
         if not ids:
             return {}
         for session in self.browse(cr, uid, ids, context=context):