diff --git a/taiga/projects/custom_attributes/api.py b/taiga/projects/custom_attributes/api.py
index 9bfc774f..2d05d186 100644
--- a/taiga/projects/custom_attributes/api.py
+++ b/taiga/projects/custom_attributes/api.py
@@ -32,6 +32,7 @@ from taiga.projects.occ.mixins import OCCResourceMixin
 
 from . import models
 from . import serializers
+from . import validators
 from . import permissions
 from . import services
 
@@ -43,6 +44,7 @@ from . import services
 class UserStoryCustomAttributeViewSet(BulkUpdateOrderMixin, BlockedByProjectMixin, ModelCrudViewSet):
     model = models.UserStoryCustomAttribute
     serializer_class = serializers.UserStoryCustomAttributeSerializer
+    validator_class = validators.UserStoryCustomAttributeValidator
     permission_classes = (permissions.UserStoryCustomAttributePermission,)
     filter_backends = (filters.CanViewProjectFilterBackend,)
     filter_fields = ("project",)
@@ -54,6 +56,7 @@ class UserStoryCustomAttributeViewSet(BulkUpdateOrderMixin, BlockedByProjectMixi
 class TaskCustomAttributeViewSet(BulkUpdateOrderMixin, BlockedByProjectMixin, ModelCrudViewSet):
     model = models.TaskCustomAttribute
     serializer_class = serializers.TaskCustomAttributeSerializer
+    validator_class = validators.TaskCustomAttributeValidator
     permission_classes = (permissions.TaskCustomAttributePermission,)
     filter_backends = (filters.CanViewProjectFilterBackend,)
     filter_fields = ("project",)
@@ -65,6 +68,7 @@ class TaskCustomAttributeViewSet(BulkUpdateOrderMixin, BlockedByProjectMixin, Mo
 class IssueCustomAttributeViewSet(BulkUpdateOrderMixin, BlockedByProjectMixin, ModelCrudViewSet):
     model = models.IssueCustomAttribute
     serializer_class = serializers.IssueCustomAttributeSerializer
+    validator_class = validators.IssueCustomAttributeValidator
     permission_classes = (permissions.IssueCustomAttributePermission,)
     filter_backends = (filters.CanViewProjectFilterBackend,)
     filter_fields = ("project",)
@@ -86,6 +90,7 @@ class BaseCustomAttributesValuesViewSet(OCCResourceMixin, HistoryResourceMixin,
 class UserStoryCustomAttributesValuesViewSet(BaseCustomAttributesValuesViewSet):
     model = models.UserStoryCustomAttributesValues
     serializer_class = serializers.UserStoryCustomAttributesValuesSerializer
+    validator_class = validators.UserStoryCustomAttributesValuesValidator
     permission_classes = (permissions.UserStoryCustomAttributesValuesPermission,)
     lookup_field = "user_story_id"
     content_object = "user_story"
@@ -99,6 +104,7 @@ class UserStoryCustomAttributesValuesViewSet(BaseCustomAttributesValuesViewSet):
 class TaskCustomAttributesValuesViewSet(BaseCustomAttributesValuesViewSet):
     model = models.TaskCustomAttributesValues
     serializer_class = serializers.TaskCustomAttributesValuesSerializer
+    validator_class = validators.TaskCustomAttributesValuesValidator
     permission_classes = (permissions.TaskCustomAttributesValuesPermission,)
     lookup_field = "task_id"
     content_object = "task"
@@ -112,6 +118,7 @@ class TaskCustomAttributesValuesViewSet(BaseCustomAttributesValuesViewSet):
 class IssueCustomAttributesValuesViewSet(BaseCustomAttributesValuesViewSet):
     model = models.IssueCustomAttributesValues
     serializer_class = serializers.IssueCustomAttributesValuesSerializer
+    validator_class = validators.IssueCustomAttributesValuesValidator
     permission_classes = (permissions.IssueCustomAttributesValuesPermission,)
     lookup_field = "issue_id"
     content_object = "issue"
diff --git a/taiga/projects/custom_attributes/serializers.py b/taiga/projects/custom_attributes/serializers.py
index 64a934f5..d4fc084e 100644
--- a/taiga/projects/custom_attributes/serializers.py
+++ b/taiga/projects/custom_attributes/serializers.py
@@ -17,131 +17,51 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-from django.apps import apps
-from django.utils.translation import ugettext_lazy as _
-
-from taiga.base.fields import JsonField
-from taiga.base.api.serializers import ValidationError
-from taiga.base.api.serializers import ModelSerializer
-
-from . import models
+from taiga.base.fields import JsonField, Field
+from taiga.base.api import serializers
 
 
 ######################################################
 # Custom Attribute Serializer
 #######################################################
 
-class BaseCustomAttributeSerializer(ModelSerializer):
-    class Meta:
-        read_only_fields = ('id',)
-        exclude = ('created_date', 'modified_date')
-
-    def _validate_integrity_between_project_and_name(self, attrs, source):
-        """
-        Check the name is not duplicated in the project. Check when:
-          - create a new one
-          - update the name
-          - update the project (move to another project)
-        """
-        data_id = attrs.get("id", None)
-        data_name = attrs.get("name", None)
-        data_project = attrs.get("project", None)
-
-        if self.object:
-            data_id = data_id or self.object.id
-            data_name = data_name or self.object.name
-            data_project = data_project or self.object.project
-
-        model = self.Meta.model
-        qs = (model.objects.filter(project=data_project, name=data_name)
-                           .exclude(id=data_id))
-        if qs.exists():
-            raise ValidationError(_("Already exists one with the same name."))
-
-        return attrs
-
-    def validate_name(self, attrs, source):
-        return self._validate_integrity_between_project_and_name(attrs, source)
-
-    def validate_project(self, attrs, source):
-        return self._validate_integrity_between_project_and_name(attrs, source)
+class BaseCustomAttributeSerializer(serializers.LightSerializer):
+    name = Field()
+    description = Field()
+    type = Field()
+    order = Field()
+    project = Field(attr="project_id")
+    created_date = Field()
+    modified_date = Field()
 
 
 class UserStoryCustomAttributeSerializer(BaseCustomAttributeSerializer):
-    class Meta(BaseCustomAttributeSerializer.Meta):
-        model = models.UserStoryCustomAttribute
+    pass
 
 
 class TaskCustomAttributeSerializer(BaseCustomAttributeSerializer):
-    class Meta(BaseCustomAttributeSerializer.Meta):
-        model = models.TaskCustomAttribute
+    pass
 
 
 class IssueCustomAttributeSerializer(BaseCustomAttributeSerializer):
-    class Meta(BaseCustomAttributeSerializer.Meta):
-        model = models.IssueCustomAttribute
+    pass
 
 
 ######################################################
 # Custom Attribute Serializer
 #######################################################
-
-
-class BaseCustomAttributesValuesSerializer(ModelSerializer):
-    attributes_values = JsonField(source="attributes_values", label="attributes values")
-    _custom_attribute_model = None
-    _container_field = None
-
-    class Meta:
-        exclude = ("id",)
-
-    def validate_attributes_values(self, attrs, source):
-        # values must be a dict
-        data_values = attrs.get("attributes_values", None)
-        if self.object:
-            data_values = (data_values or self.object.attributes_values)
-
-        if type(data_values) is not dict:
-            raise ValidationError(_("Invalid content. It must be {\"key\": \"value\",...}"))
-
-        # Values keys must be in the container object project
-        data_container = attrs.get(self._container_field, None)
-        if data_container:
-            project_id = data_container.project_id
-        elif self.object:
-            project_id = getattr(self.object, self._container_field).project_id
-        else:
-            project_id = None
-
-        values_ids = list(data_values.keys())
-        qs = self._custom_attribute_model.objects.filter(project=project_id,
-                                                         id__in=values_ids)
-        if qs.count() != len(values_ids):
-            raise ValidationError(_("It contain invalid custom fields."))
-
-        return attrs
+class BaseCustomAttributesValuesSerializer(serializers.LightSerializer):
+    attributes_values = Field()
+    version = Field()
 
 
 class UserStoryCustomAttributesValuesSerializer(BaseCustomAttributesValuesSerializer):
-    _custom_attribute_model = models.UserStoryCustomAttribute
-    _container_model = "userstories.UserStory"
-    _container_field = "user_story"
-
-    class Meta(BaseCustomAttributesValuesSerializer.Meta):
-        model = models.UserStoryCustomAttributesValues
+    user_story = Field(attr="user_story.id")
 
 
-class TaskCustomAttributesValuesSerializer(BaseCustomAttributesValuesSerializer, ModelSerializer):
-    _custom_attribute_model = models.TaskCustomAttribute
-    _container_field = "task"
-
-    class Meta(BaseCustomAttributesValuesSerializer.Meta):
-        model = models.TaskCustomAttributesValues
+class TaskCustomAttributesValuesSerializer(BaseCustomAttributesValuesSerializer):
+    task = Field(attr="task.id")
 
 
-class IssueCustomAttributesValuesSerializer(BaseCustomAttributesValuesSerializer, ModelSerializer):
-    _custom_attribute_model = models.IssueCustomAttribute
-    _container_field = "issue"
-
-    class Meta(BaseCustomAttributesValuesSerializer.Meta):
-        model = models.IssueCustomAttributesValues
+class IssueCustomAttributesValuesSerializer(BaseCustomAttributesValuesSerializer):
+    issue = Field(attr="issue.id")
diff --git a/taiga/projects/custom_attributes/validators.py b/taiga/projects/custom_attributes/validators.py
new file mode 100644
index 00000000..506c040c
--- /dev/null
+++ b/taiga/projects/custom_attributes/validators.py
@@ -0,0 +1,146 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2014-2016 Andrey Antukh <niwi@niwi.nz>
+# Copyright (C) 2014-2016 Jesús Espino <jespinog@gmail.com>
+# Copyright (C) 2014-2016 David Barragán <bameda@dbarragan.com>
+# Copyright (C) 2014-2016 Alejandro Alonso <alejandro.alonso@kaleidos.net>
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+from django.utils.translation import ugettext_lazy as _
+
+from taiga.base.fields import JsonField
+from taiga.base.api.serializers import ValidationError
+from taiga.base.api.validators import ModelValidator
+
+from . import models
+
+
+######################################################
+# Custom Attribute Validator
+#######################################################
+
+class BaseCustomAttributeValidator(ModelValidator):
+    class Meta:
+        read_only_fields = ('id',)
+        exclude = ('created_date', 'modified_date')
+
+    def _validate_integrity_between_project_and_name(self, attrs, source):
+        """
+        Check the name is not duplicated in the project. Check when:
+          - create a new one
+          - update the name
+          - update the project (move to another project)
+        """
+        data_id = attrs.get("id", None)
+        data_name = attrs.get("name", None)
+        data_project = attrs.get("project", None)
+
+        if self.object:
+            data_id = data_id or self.object.id
+            data_name = data_name or self.object.name
+            data_project = data_project or self.object.project
+
+        model = self.Meta.model
+        qs = (model.objects.filter(project=data_project, name=data_name)
+                           .exclude(id=data_id))
+        if qs.exists():
+            raise ValidationError(_("Already exists one with the same name."))
+
+        return attrs
+
+    def validate_name(self, attrs, source):
+        return self._validate_integrity_between_project_and_name(attrs, source)
+
+    def validate_project(self, attrs, source):
+        return self._validate_integrity_between_project_and_name(attrs, source)
+
+
+class UserStoryCustomAttributeValidator(BaseCustomAttributeValidator):
+    class Meta(BaseCustomAttributeValidator.Meta):
+        model = models.UserStoryCustomAttribute
+
+
+class TaskCustomAttributeValidator(BaseCustomAttributeValidator):
+    class Meta(BaseCustomAttributeValidator.Meta):
+        model = models.TaskCustomAttribute
+
+
+class IssueCustomAttributeValidator(BaseCustomAttributeValidator):
+    class Meta(BaseCustomAttributeValidator.Meta):
+        model = models.IssueCustomAttribute
+
+
+######################################################
+# Custom Attribute Validator
+#######################################################
+
+
+class BaseCustomAttributesValuesValidator(ModelValidator):
+    attributes_values = JsonField(source="attributes_values", label="attributes values")
+    _custom_attribute_model = None
+    _container_field = None
+
+    class Meta:
+        exclude = ("id",)
+
+    def validate_attributes_values(self, attrs, source):
+        # values must be a dict
+        data_values = attrs.get("attributes_values", None)
+        if self.object:
+            data_values = (data_values or self.object.attributes_values)
+
+        if type(data_values) is not dict:
+            raise ValidationError(_("Invalid content. It must be {\"key\": \"value\",...}"))
+
+        # Values keys must be in the container object project
+        data_container = attrs.get(self._container_field, None)
+        if data_container:
+            project_id = data_container.project_id
+        elif self.object:
+            project_id = getattr(self.object, self._container_field).project_id
+        else:
+            project_id = None
+
+        values_ids = list(data_values.keys())
+        qs = self._custom_attribute_model.objects.filter(project=project_id,
+                                                         id__in=values_ids)
+        if qs.count() != len(values_ids):
+            raise ValidationError(_("It contain invalid custom fields."))
+
+        return attrs
+
+
+class UserStoryCustomAttributesValuesValidator(BaseCustomAttributesValuesValidator):
+    _custom_attribute_model = models.UserStoryCustomAttribute
+    _container_model = "userstories.UserStory"
+    _container_field = "user_story"
+
+    class Meta(BaseCustomAttributesValuesValidator.Meta):
+        model = models.UserStoryCustomAttributesValues
+
+
+class TaskCustomAttributesValuesValidator(BaseCustomAttributesValuesValidator, ModelValidator):
+    _custom_attribute_model = models.TaskCustomAttribute
+    _container_field = "task"
+
+    class Meta(BaseCustomAttributesValuesValidator.Meta):
+        model = models.TaskCustomAttributesValues
+
+
+class IssueCustomAttributesValuesValidator(BaseCustomAttributesValuesValidator, ModelValidator):
+    _custom_attribute_model = models.IssueCustomAttribute
+    _container_field = "issue"
+
+    class Meta(BaseCustomAttributesValuesValidator.Meta):
+        model = models.IssueCustomAttributesValues