diff --git a/inventory.py b/inventory.py
index 4371e129ea..6d1277ddef 100644
--- a/inventory.py
+++ b/inventory.py
@@ -1,5 +1,7 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level
 #of this repository contains the full copyright notices and license terms.
+from sql import Null
+
 from trytond.model import Workflow, ModelView, ModelSQL, fields
 from trytond.pyson import Not, Equal, Eval, Or, Bool
 from trytond import backend
@@ -273,7 +275,7 @@ class InventoryLine(ModelSQL, ModelView):
         # Migration from 3.0: use Move origin
         if table.column_exist('move'):
             cursor.execute(*sql_table.select(sql_table.id, sql_table.move,
-                    where=sql_table.move != None))
+                    where=sql_table.move != Null))
             for line_id, move_id in cursor.fetchall():
                 cursor.execute(*move_table.update(
                         columns=[move_table.origin],
diff --git a/move.py b/move.py
index 2eb8151547..5c90c257c3 100644
--- a/move.py
+++ b/move.py
@@ -4,7 +4,8 @@ import datetime
 import operator
 from decimal import Decimal
 from functools import partial
-from sql import Literal, Union, Column
+
+from sql import Literal, Union, Column, Null
 from sql.aggregate import Sum
 from sql.conditionals import Coalesce
 from sql.operators import Concat
@@ -345,7 +346,7 @@ class Move(Workflow, ModelSQL, ModelView):
                         columns=[sql_table.shipment],
                         values=[Concat(model + ',',
                                 Column(sql_table, column))],
-                        where=Column(sql_table, column) != None))
+                        where=Column(sql_table, column) != Null))
                 table.drop_column(column)
 
         # Add index on create_date
@@ -889,7 +890,7 @@ class Move(Workflow, ModelSQL, ModelView):
                         context.get('stock_assign') and 'assigned' or 'done'])
                 & (
                     (
-                        (move.effective_date == None)
+                        (move.effective_date == Null)
                         & (move.planned_date <= context['stock_date_end'])
                         )
                     | (move.effective_date <= context['stock_date_end'])
@@ -905,7 +906,7 @@ class Move(Workflow, ModelSQL, ModelView):
                             or 'done'])
                     & (
                         (
-                            (move.effective_date == None)
+                            (move.effective_date == Null)
                             & (move.planned_date <= today)
                             )
                         | (move.effective_date <= today)
@@ -914,7 +915,7 @@ class Move(Workflow, ModelSQL, ModelView):
                 | (move.state.in_(['done', 'assigned', 'draft'])
                     & (
                         (
-                            (move.effective_date == None)
+                            (move.effective_date == Null)
                             & (Coalesce(move.planned_date, datetime.date.max)
                                 <= context['stock_date_end'])
                             & (Coalesce(move.planned_date, datetime.date.max)
@@ -934,11 +935,11 @@ class Move(Workflow, ModelSQL, ModelView):
                     move.state.in_(['done', 'assigned', 'draft'])
                     & (
                         (
-                            (move.effective_date == None)
+                            (move.effective_date == Null)
                             & (
                                 (move.planned_date >=
                                     context['stock_date_start'])
-                                | (move.planned_date == None)
+                                | (move.planned_date == Null)
                                 )
                             )
                         | (move.effective_date >= context['stock_date_start'])
@@ -950,10 +951,10 @@ class Move(Workflow, ModelSQL, ModelView):
                         move.state.in_(['done', 'assigned', 'draft'])
                         & (
                             (
-                                (move.effective_date == None)
+                                (move.effective_date == Null)
                                 & (
                                     (move.planned_date >= today)
-                                    | (move.planned_date == None)
+                                    | (move.planned_date == Null)
                                     )
                                 )
                             | (move.effective_date >= today)
@@ -965,14 +966,14 @@ class Move(Workflow, ModelSQL, ModelView):
                                 or 'done'])
                         & (
                             (
-                                (move.effective_date == None)
+                                (move.effective_date == Null)
                                 & (
                                     (
                                         (move.planned_date >=
                                             context['stock_date_start'])
                                         & (move.planned_date < today)
                                         )
-                                    | (move.planned_date == None)
+                                    | (move.planned_date == Null)
                                     )
                                 )
                             | (
diff --git a/product.py b/product.py
index f0e8fdfc17..67c166cceb 100644
--- a/product.py
+++ b/product.py
@@ -2,7 +2,8 @@
 #this repository contains the full copyright notices and license terms.
 import datetime
 from decimal import Decimal
-from sql import Literal
+
+from sql import Literal, Null
 from sql.aggregate import Max
 from sql.functions import Now
 from sql.conditionals import Coalesce
@@ -261,7 +262,7 @@ class ProductQuantitiesByWarehouse(ModelSQL, ModelView):
             where=(move.product == product_id)
             & (move.from_location.in_(warehouse_query)
                 | move.to_location.in_(warehouse_query))
-            & (Coalesce(move.effective_date, move.planned_date) != None),
+            & (Coalesce(move.effective_date, move.planned_date) != Null),
             group_by=(date_column, move.product))
 
     @classmethod
diff --git a/setup.py b/setup.py
index 433d0313a9..d89c2aa29f 100644
--- a/setup.py
+++ b/setup.py
@@ -41,7 +41,7 @@ if minor_version % 2:
         'hg+http://hg.tryton.org/modules/%s#egg=%s-%s' % (
             name[8:], name, version))
 
-requires = ['python-sql']
+requires = ['python-sql >= 0.4']
 for dep in info.get('depends', []):
     if not re.match(r'(ir|res|webdav)(\W|$)', dep):
         requires.append(get_require_version('trytond_%s' % dep))