diff --git a/openslides/assignments/serializers.py b/openslides/assignments/serializers.py
index 8b67ea46b..1f13aee6d 100644
--- a/openslides/assignments/serializers.py
+++ b/openslides/assignments/serializers.py
@@ -1,6 +1,7 @@
 from django.db import transaction
 from django.utils.translation import ugettext as _
 
+from openslides.poll.serializers import default_votes_validator
 from openslides.utils.rest_api import (
     DictField,
     IntegerField,
@@ -106,6 +107,7 @@ class AssignmentAllPollSerializer(ModelSerializer):
             'has_votes',
             'assignment')  # js-data needs the assignment-id in the nested object to define relations.
         read_only_fields = ('yesnoabstain',)
+        validators = (default_votes_validator,)
 
     def get_has_votes(self, obj):
         """
diff --git a/openslides/motions/serializers.py b/openslides/motions/serializers.py
index 58c2ca1b4..0474b23ae 100644
--- a/openslides/motions/serializers.py
+++ b/openslides/motions/serializers.py
@@ -1,6 +1,7 @@
 from django.db import transaction
 from django.utils.translation import ugettext as _
 
+from openslides.poll.serializers import default_votes_validator
 from openslides.utils.rest_api import (
     CharField,
     DictField,
@@ -115,6 +116,7 @@ class MotionPollSerializer(ModelSerializer):
             'votescast',
             'votes',
             'has_votes')
+        validators = (default_votes_validator,)
 
     def get_yes(self, obj):
         try:
diff --git a/openslides/poll/serializers.py b/openslides/poll/serializers.py
new file mode 100644
index 000000000..82d4a6a6f
--- /dev/null
+++ b/openslides/poll/serializers.py
@@ -0,0 +1,15 @@
+from django.utils.translation import ugettext as _
+
+from ..utils.rest_api import ValidationError
+
+
+def default_votes_validator(data):
+    """
+    Use this validator in your poll serializer. It checks that the values
+    for the default votes (see models.CollectDefaultVotesMixin) are greater
+    than or equal to -2.
+    """
+    for key in data:
+        if key in ('votesvalid', 'votesinvalid', 'votescast') and data[key] < -2:
+            raise ValidationError({'detail': _('Value for {} must not be less than -2').format(key)})
+    return data
diff --git a/tests/integration/assignments/test_viewset.py b/tests/integration/assignments/test_viewset.py
index 75027d1f0..5c3ff649c 100644
--- a/tests/integration/assignments/test_viewset.py
+++ b/tests/integration/assignments/test_viewset.py
@@ -1,5 +1,6 @@
 from django.contrib.auth import get_user_model
 from django.core.urlresolvers import reverse
+from rest_framework import status
 from rest_framework.test import APIClient
 
 from openslides.assignments.models import Assignment
@@ -273,3 +274,36 @@ class MarkElectedOtherUser(TestCase):
 
         self.assertEqual(response.status_code, 200)
         self.assertFalse(Assignment.objects.get(pk=self.assignment.pk).elected.filter(username='test_user_Oonei3rahji5jugh1eev').exists())
+
+
+class UpdateAssignmentPoll(TestCase):
+    """
+    Tests updating polls of assignments.
+    """
+    def setUp(self):
+        self.client = APIClient()
+        self.client.login(username='admin', password='admin')
+        self.assignment = Assignment.objects.create(title='test_assignment_ohneivoh9caiB8Yiungo', open_posts=1)
+        self.assignment.set_candidate(get_user_model().objects.get(username='admin'))
+        self.poll = self.assignment.create_poll()
+
+    def test_invalid_votesvalid_value(self):
+        response = self.client.put(
+            reverse('assignmentpoll-detail', args=[self.poll.pk]),
+            {'assignment_id': self.assignment.pk,
+             'votesvalid': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_invalid_votesinvalid_value(self):
+        response = self.client.put(
+            reverse('assignmentpoll-detail', args=[self.poll.pk]),
+            {'assignment_id': self.assignment.pk,
+             'votesinvalid': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_invalid_votescast_value(self):
+        response = self.client.put(
+            reverse('assignmentpoll-detail', args=[self.poll.pk]),
+            {'assignment_id': self.assignment.pk,
+             'votescast': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
diff --git a/tests/integration/motions/test_viewset.py b/tests/integration/motions/test_viewset.py
index 3f2abff4d..81c14df24 100644
--- a/tests/integration/motions/test_viewset.py
+++ b/tests/integration/motions/test_viewset.py
@@ -360,3 +360,38 @@ class SetState(TestCase):
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(response.data, {'detail': 'The state of the motion was set to submitted.'})
         self.assertEqual(Motion.objects.get(pk=self.motion.pk).state.name, 'submitted')
+
+
+class UpdateMotionPoll(TestCase):
+    """
+    Tests updating polls of motions.
+    """
+    def setUp(self):
+        self.client = APIClient()
+        self.client.login(username='admin', password='admin')
+        self.motion = Motion(
+            title='test_title_Aiqueigh2dae9phabiqu',
+            text='test_text_Neekoh3zou6li5rue8iL')
+        self.motion.save()
+        self.poll = self.motion.create_poll()
+
+    def test_invalid_votesvalid_value(self):
+        response = self.client.put(
+            reverse('motionpoll-detail', args=[self.poll.pk]),
+            {'motion_id': self.motion.pk,
+             'votesvalid': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_invalid_votesinvalid_value(self):
+        response = self.client.put(
+            reverse('motionpoll-detail', args=[self.poll.pk]),
+            {'motion_id': self.motion.pk,
+             'votesinvalid': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
+    def test_invalid_votescast_value(self):
+        response = self.client.put(
+            reverse('motionpoll-detail', args=[self.poll.pk]),
+            {'motion_id': self.motion.pk,
+             'votescast': '-3'})
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)