diff --git a/trytond/model/modelsql.py b/trytond/model/modelsql.py
index 2feb55454b..0cbd4b0b25 100644
--- a/trytond/model/modelsql.py
+++ b/trytond/model/modelsql.py
@@ -1835,15 +1835,21 @@ class ModelSQL(ModelStorage):
             else:
                 if (arg[2] is False or arg[2] is None) and (arg[1] == '='):
                     if column._type == 'boolean':
-                        qu1.append('("%s"."%s" = %%s)' % \
-                                (table._table, arg[0]))
+                        qu1.append('(("%s"."%s" = %%s) OR ("%s"."%s" IS NULL))'
+                            % (table._table, arg[0], table._table, arg[0]))
                         qu2.append(False)
                     else:
                         qu1.append('("%s"."%s" IS NULL)' % \
-                                (table._table, arg[0]))
-                elif (arg[2] is False or arg[2] is None) and (arg[1] == '!='):
-                    qu1.append('("%s"."%s" IS NOT NULL)' % \
                             (table._table, arg[0]))
+                elif (arg[2] is False or arg[2] is None) and (arg[1] == '!='):
+                    if column._type == 'boolean':
+                        qu1.append('(("%s"."%s" != %%s) '
+                            'AND ("%s"."%s" IS NOT NULL))'
+                            % (table._table, arg[0], table._table, arg[0]))
+                        qu2.append(False)
+                    else:
+                        qu1.append('("%s"."%s" IS NOT NULL)' % \
+                                (table._table, arg[0]))
                 else:
                     if arg[0] == 'id':
                         qu1.append('("%s"."%s" %s %%s)' % \
diff --git a/trytond/tests/test_fields.py b/trytond/tests/test_fields.py
index 71d2a193c5..564d38f88f 100644
--- a/trytond/tests/test_fields.py
+++ b/trytond/tests/test_fields.py
@@ -170,6 +170,23 @@ class FieldsTestCase(unittest.TestCase):
             boolean3_id = self.boolean.create({})
             self.assert_(boolean3_id)
 
+            # Test search with NULL value
+            boolean4_id = self.boolean.create({
+                    'boolean': None,
+                    })
+            self.assert_(boolean4_id)
+
+            boolean_ids = self.boolean.search([
+                    ('boolean', '=', False),
+                    ])
+            self.assertEqual(boolean_ids,
+                [boolean2_id, boolean3_id, boolean4_id])
+
+            boolean_ids = self.boolean.search([
+                    ('boolean', '!=', False),
+                    ])
+            self.assertEqual(boolean_ids, [boolean1_id])
+
             boolean3 = self.boolean.read(boolean3_id, ['boolean'])
             self.assert_(boolean3['boolean'] == False)