diff --git a/models/res_partner_id_number.py b/models/res_partner_id_number.py
index aae67dd40..2f0c621aa 100644
--- a/models/res_partner_id_number.py
+++ b/models/res_partner_id_number.py
@@ -16,7 +16,7 @@ class ResPartnerIdNumber(models.Model):
     _name = "res.partner.id_number"
     _order = "name"
 
-    @api.constrains('name')
+    @api.constrains('name', 'category_id')
     def validate_id_number(self):
         self.category_id.validate_id_number(self)
 
diff --git a/tests/test_partner_identification.py b/tests/test_partner_identification.py
index 48d8dde40..d46a243c4 100644
--- a/tests/test_partner_identification.py
+++ b/tests/test_partner_identification.py
@@ -21,13 +21,13 @@ class TestPartnerIdentificationBase(common.TransactionCase):
         partner_1 = self.env.ref('base.res_partner_1')
         self.assertEquals(len(partner_1.id_numbers), 0)
         with self.assertRaises(IntegrityError), self.cr.savepoint():
-            partner_1.id_numbers = [(0, 0,  {
+            partner_1.write({'id_numbers': [(0, 0,  {
                 'name': '1234',
-            })]
-        partner_1.id_numbers = [(0, 0,  {
+            })]})
+        partner_1.write({'id_numbers': [(0, 0,  {
             'name': '1234',
-            'category_id': partner_id_category
-        })]
+            'category_id': partner_id_category.id
+        })]})
         self.assertEquals(len(partner_1.id_numbers), 1)
         self.assertEquals(partner_1.id_numbers.name, '1234')
 
@@ -45,17 +45,31 @@ if id_number.name != '1234':
         })
         partner_1 = self.env.ref('base.res_partner_1')
         with self.assertRaises(ValidationError), self.cr.savepoint():
-            partner_1.id_numbers = [(0, 0,  {
+            partner_1.write({'id_numbers': [(0, 0,  {
                 'name': '01234',
-                'category_id': partner_id_category
-            })]
-        partner_1.id_numbers = [(0, 0,  {
+                'category_id': partner_id_category.id
+            })]})
+        partner_1.write({'id_numbers': [(0, 0,  {
             'name': '1234',
-            'category_id': partner_id_category
-        })]
+            'category_id': partner_id_category.id
+        })]})
         self.assertEquals(len(partner_1.id_numbers), 1)
         self.assertEquals(partner_1.id_numbers.name, '1234')
 
+        partner_id_category2 = self.env['res.partner.id_category'].create({
+            'code': 'id_code2',
+            'name': 'id_name2',
+            'validation_code': """
+if id_number.name != '1235':
+    failed = True
+"""})
+        # check that the constrains is also checked when we change the
+        # associated category
+        with self.assertRaises(ValidationError), self.cr.savepoint():
+            partner_1.id_numbers.write({
+                'category_id': partner_id_category2.id
+            })
+
     def test_bad_calidation_code(self):
         partner_id_category = self.env['res.partner.id_category'].create({
             'code': 'id_code',
@@ -67,7 +81,7 @@ if id_number.name != '1234' #  missing :
         })
         partner_1 = self.env.ref('base.res_partner_1')
         with self.assertRaises(ValidationError):
-            partner_1.id_numbers = [(0, 0,  {
+            partner_1.write({'id_numbers': [(0, 0,  {
                 'name': '1234',
-                'category_id': partner_id_category
-            })]
+                'category_id': partner_id_category.id
+            })]})