diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 0c0da84e..9898df05 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -5,7 +5,9 @@ ChangeLog
 master (unreleased)
 ===================
 
-- Nothing here yet
+* Enforce unicity of keys in NestedListSerializers (#202)
+* Define __unicode__ and __str__ on models (#200)
+* Fix regression on presets_lists endpoint (#199)
 
 Release 0.8.1 (2017-03-07)
 ==========================
diff --git a/demo/tests/tests_integration.py b/demo/tests/tests_integration.py
index 265e3642..d4ad5690 100644
--- a/demo/tests/tests_integration.py
+++ b/demo/tests/tests_integration.py
@@ -86,6 +86,15 @@ def test_simple(self):
                 field.accesses.filter(access_id=access, level=level).exists()
             )
 
+    def test_fields_slug(self):
+        data = deepcopy(form_data)
+        # duplicate field
+        data['fields'] *= 2
+        res = self.client.post(
+            reverse('formidable:form_create'), data, format='json'
+        )
+        self.assertEquals(res.status_code, 400)
+
     def test_with_items_in_fields(self):
         initial_count = Formidable.objects.count()
         res = self.client.post(
@@ -179,6 +188,17 @@ def test_create_field_on_update(self):
         self.assertEquals(form.pk, self.form.pk)
         self.assertEquals(form.fields.count(), 2)
 
+    def test_duplicate_items_update(self):
+        # create a form with items
+        data = deepcopy(form_data_items)
+        res = self.client.put(self.edit_url, data, format='json')
+        self.assertEquals(res.status_code, 200)
+        # update items with duplicate entries
+        data['fields'] *= 2
+        res = self.client.put(self.edit_url, data, format='json')
+        # expect validation error
+        self.assertEquals(res.status_code, 400)
+
     def test_delete_field_on_update(self):
         self.form.fields.create(
             type_id='text', slug='textslug', label='mytext',
diff --git a/formidable/serializers/access.py b/formidable/serializers/access.py
index 91a0ebda..eac1a4c4 100644
--- a/formidable/serializers/access.py
+++ b/formidable/serializers/access.py
@@ -36,6 +36,7 @@ class AccessListSerializer(NestedListSerializer):
     parent_name = 'field_id'
 
     def validate(self, data):
+        data = super(AccessListSerializer, self).validate(data)
         accesses_id = [accesses['access_id'] for accesses in data]
 
         for access in get_accesses():
diff --git a/formidable/serializers/fields.py b/formidable/serializers/fields.py
index 1bef7754..8feaa804 100644
--- a/formidable/serializers/fields.py
+++ b/formidable/serializers/fields.py
@@ -41,6 +41,8 @@ def validate(self, validated_data):
         order before the update/create method sorts the validated data
         by id.
         """
+        validated_data = super(FieldListSerializer, self).validate(
+                validated_data)
         for index, data in enumerate(validated_data):
             data['order'] = index
 
diff --git a/formidable/serializers/list.py b/formidable/serializers/list.py
index c52758a4..91e10e1d 100644
--- a/formidable/serializers/list.py
+++ b/formidable/serializers/list.py
@@ -4,6 +4,7 @@
 
 import logging
 
+from rest_framework.exceptions import ValidationError
 from rest_framework.serializers import ListSerializer
 
 logger = logging.getLogger(__name__)
@@ -50,6 +51,21 @@ def _extract_id(self, qs, validated_data):
         deleted_ids = db_ids - validated_ids
         return created_ids, updated_ids, deleted_ids
 
+    def validate(self, data):
+        """
+        ensure that field_id is unique among children
+        """
+        data = super(NestedListSerializer, self).validate(data)
+
+        if self.field_id:
+            if len(data) != len(set(f[self.field_id] for f in data)):
+                msg = 'The fields {field_id} must make a unique set.'.format(
+                        field_id=self.field_id
+                )
+                raise ValidationError(msg, code='unique')
+
+        return data
+
 
 class NestedListSerializerDummyUpdate(NestedListSerializer):