diff --git a/trytond/doc/topics/domain.rst b/trytond/doc/topics/domain.rst
index f7c9be42cf..f51b09a94e 100644
--- a/trytond/doc/topics/domain.rst
+++ b/trytond/doc/topics/domain.rst
@@ -40,6 +40,7 @@ by this pattern::
     .. note::
       Negative operators match records for which any of the field before the
       last dot is empty.
+      Except if the operand is or contains ``None``.
 
 .. warning::
     For :class:`trytond.model.fields.Reference`, an extra ending clause is
diff --git a/trytond/trytond/model/fields/many2one.py b/trytond/trytond/model/fields/many2one.py
index 1c31118e0c..42708901d4 100644
--- a/trytond/trytond/model/fields/many2one.py
+++ b/trytond/trytond/model/fields/many2one.py
@@ -236,7 +236,10 @@ class Many2One(Field):
                 target_domain = [target_domain, rule_domain]
             _, expression = Target.search_domain(
                 target_domain, tables=target_tables)
-        if operator.startswith('not') or operator == '!=':
+        if ((operator.startswith('not') and not (
+                        operator == 'not in'
+                        and None in value))
+                or (operator == '!=' and value is not None)):
             expression |= column == Null
         return expression
 
diff --git a/trytond/trytond/model/fields/reference.py b/trytond/trytond/model/fields/reference.py
index 33d47d7350..4fdd2707ba 100644
--- a/trytond/trytond/model/fields/reference.py
+++ b/trytond/trytond/model/fields/reference.py
@@ -189,7 +189,10 @@ class Reference(SelectionMixin, Field):
                     Position(',', column) + Literal(1)),
                 Model.id.sql_type().base).in_(query)
             & column.ilike(target + ',%'))
-        if operator.startswith('not') or operator == '!=':
+        if ((operator.startswith('not') and not (
+                        operator == 'not in'
+                        and None in value))
+                or (operator == '!=' and value is not None)):
             expression |= column == Null
         return expression
 
diff --git a/trytond/trytond/tests/test_field_many2one.py b/trytond/trytond/tests/test_field_many2one.py
index 6b7ca8d118..ce71e7e3c6 100644
--- a/trytond/trytond/tests/test_field_many2one.py
+++ b/trytond/trytond/tests/test_field_many2one.py
@@ -485,6 +485,21 @@ class FieldMany2OneTestCase(unittest.TestCase):
                 ])
         self.assertListEqual(result, [record])
 
+        result = Many2One.search([
+                ('many2one.value', '!=', None),
+                ])
+        self.assertListEqual(result, [])
+
+        result = Many2One.search([
+                ('many2one.value', 'not in', [1]),
+                ])
+        self.assertListEqual(result, [record])
+
+        result = Many2One.search([
+                ('many2one.value', 'not in', [1, None]),
+                ])
+        self.assertListEqual(result, [])
+
     @with_transaction()
     def test_context_attribute(self):
         "Test context on many2one attribute"
diff --git a/trytond/trytond/tests/test_field_reference.py b/trytond/trytond/tests/test_field_reference.py
index ae36dc8c31..96d9bc0432 100644
--- a/trytond/trytond/tests/test_field_reference.py
+++ b/trytond/trytond/tests/test_field_reference.py
@@ -373,6 +373,25 @@ class FieldReferenceTestCase(unittest.TestCase):
 
         self.assertListEqual(result, [reference])
 
+        result = Reference.search([
+                ('reference.name', '!=', None, Target.__name__),
+                ])
+
+        self.assertListEqual(result, [])
+
+        result = Reference.search([
+                ('reference.name', 'not in', ["Target"], Target.__name__),
+                ])
+
+        self.assertListEqual(result, [reference])
+
+        result = Reference.search([
+                ('reference.name', 'not in', ["Target", None],
+                    Target.__name__),
+                ])
+
+        self.assertListEqual(result, [])
+
     @with_transaction()
     def test_write_string(self):
         "Test write reference string"