diff --git a/openerp/addons/base/tests/test_expression.py b/openerp/addons/base/tests/test_expression.py
index c43dda85e9b..49bc7d57ca1 100644
--- a/openerp/addons/base/tests/test_expression.py
+++ b/openerp/addons/base/tests/test_expression.py
@@ -114,6 +114,12 @@ class test_expression(common.TransactionCase):
         # Test2: inheritance + relational fields
         user_ids = users_obj.search(cr, uid, [('child_ids.name', 'like', 'test_B')])
         self.assertEqual(set(user_ids), set([b1]), 'searching through inheritance failed')
+        
+        # Special =? operator mean "is equal if right is set, otherwise always True"
+        user_ids = users_obj.search(cr, uid, [('name', 'like', 'test'), ('parent_id', '=?', False)])
+        self.assertEqual(set(user_ids), set([a, b1, b2]), '(x =? False) failed')
+        user_ids = users_obj.search(cr, uid, [('name', 'like', 'test'), ('parent_id', '=?', b1_user.partner_id.id)])
+        self.assertEqual(set(user_ids), set([b2]), '(x =? id) failed')
 
     def test_20_auto_join(self):
         registry, cr, uid = self.registry, self.cr, self.uid
diff --git a/openerp/osv/expression.py b/openerp/osv/expression.py
index bf02c12a228..ba00c2caa91 100644
--- a/openerp/osv/expression.py
+++ b/openerp/osv/expression.py
@@ -598,6 +598,15 @@ class ExtendedLeaf(object):
         self.leaf = normalize_leaf(self.leaf)
         return True
 
+def create_substitution_leaf(leaf, new_elements, new_model=None):
+    """ From a leaf, create a new leaf (based on the new_elements tuple
+        and new_model), that will have the same join context. Used to
+        insert equivalent leafs in the processing stack. """
+    if new_model is None:
+        new_model = leaf.model
+    new_join_context = [tuple(context) for context in leaf.join_context]
+    new_leaf = ExtendedLeaf(new_elements, new_model, join_context=new_join_context)
+    return new_leaf
 
 class expression(object):
     """ Parse a domain expression
@@ -715,16 +724,6 @@ class expression(object):
                     return ids + recursive_children(ids2, model, parent_field)
                 return [(left, 'in', recursive_children(ids, left_model, parent or left_model._parent_name))]
 
-        def create_substitution_leaf(leaf, new_elements, new_model=None):
-            """ From a leaf, create a new leaf (based on the new_elements tuple
-                and new_model), that will have the same join context. Used to
-                insert equivalent leafs in the processing stack. """
-            if new_model is None:
-                new_model = leaf.model
-            new_join_context = [tuple(context) for context in leaf.join_context]
-            new_leaf = ExtendedLeaf(new_elements, new_model, join_context=new_join_context)
-            return new_leaf
-
         def pop():
             """ Pop a leaf to process. """
             return self.stack.pop()
@@ -1153,7 +1152,8 @@ class expression(object):
                 params = []
             else:
                 # '=?' behaves like '=' in other cases
-                query, params = self.__leaf_to_sql((left, '=', right), model)
+                query, params = self.__leaf_to_sql(
+                    create_substitution_leaf(eleaf, (left, '=', right), model))
 
         elif left == 'id':
             query = '%s.id %s %%s' % (table_alias, operator)