diff --git a/openslides/users/exceptions.py b/openslides/users/exceptions.py
deleted file mode 100644
index 185aa383d..000000000
--- a/openslides/users/exceptions.py
+++ /dev/null
@@ -1,5 +0,0 @@
-from ..utils.exceptions import OpenSlidesError
-
-
-class UsersError(OpenSlidesError):
-    pass
diff --git a/openslides/users/migrations/0004_groups.py b/openslides/users/migrations/0004_groups.py
index 99fefe4ec..262526b0d 100644
--- a/openslides/users/migrations/0004_groups.py
+++ b/openslides/users/migrations/0004_groups.py
@@ -2,47 +2,53 @@
 # Generated by Django 1.9.7 on 2016-08-01 14:54
 from __future__ import unicode_literals
 
-from django.core.exceptions import ObjectDoesNotExist
-from django.db import migrations
+from django.db import migrations, models
 
 
 def migrate_groups_and_user_permissions(apps, schema_editor):
     """
     This function migrates the database to the new groups logic:
-    - Rename Group 'Anonymous' (pk=1) to 'Default'
-    - Rename Group 'Registered users' (pk=2) to 'Previous group Registered'
+    - Rename group 'Anonymous' (pk=1) to 'Default'
+    - Rename group 'Registered users' (pk=2) to 'Previous group Registered'
     - Add all users who are not in any group to this group (pk=2)
-    - Add all permissions of 'Previous group Registered' to all other groups (exclude 'Default')
+    - Add all permissions of 'Previous group Registered' to all other groups (except 'Default')
 
-    But only do this migration if:
-    - there are groups in the database
-    - the name of the first group is 'Guests'.
+    But only run this migration if:
+    - there are groups in the database,
+    - the name of the first group is 'Guests',
+    - the name of the second group is 'Registered users'.
     """
+    # Disconnect autoupdate. We do not want to trigger it here.
+    models.signals.post_save.disconnect(dispatch_uid='inform_changed_data_receiver')
+
     User = apps.get_model('users', 'User')
     Group = apps.get_model('auth', 'Group')
 
-    if Group.objects.exists():
-        try:
-            group_default = Group.objects.filter(pk=1)
-            if group_default.get().name == 'Guests':
-                group_default.update(name='Default')
+    try:
+        group_default = Group.objects.get(pk=1)
+        group_registered = Group.objects.get(pk=2)
+    except Group.DoesNotExist:
+        # One of the groups does not exist. Just do nothing.
+        pass
+    else:
+        if group_default.name == 'Guests' and group_registered.name == 'Registered users':
+            # Rename groups pk 1 and 2.
+            group_default.name = 'Default'
+            group_default.save()
+            group_registered.name = 'Previous group Registered'
+            group_registered.save()
 
-                group_old_registered = Group.objects.filter(pk=2)
-                group_old_registered.update(name='Previous group Registered')
-                group_old_registered = group_old_registered.get()
+            # Move users without groups to group pk 2.
+            users = User.objects.all()
+            for user in users:
+                if not user.groups.exists():
+                    user.groups.add(group_registered)
 
-                users = User.objects.all()
-                for user in users:
-                    if not user.groups.exists():
-                        user.groups.add(group_old_registered.pk)
-
-                groups = Group.objects.filter(pk__gt=2)
-                for group in groups:
-                    for permission in group_old_registered.permissions.all():
-                        group.permissions.add(permission)
-        except ObjectDoesNotExist:
-            # If the first or second group doesn't exists, just pass this migraition
-            pass
+            # Copy permissions of group pk 2 to all other groups except pk 1.
+            groups = Group.objects.filter(pk__gt=2)
+            for group in groups:
+                for permission in group_registered.permissions.all():
+                    group.permissions.add(permission)
 
 
 class Migration(migrations.Migration):
diff --git a/openslides/users/signals.py b/openslides/users/signals.py
index 9700f718c..8d6437764 100644
--- a/openslides/users/signals.py
+++ b/openslides/users/signals.py
@@ -12,7 +12,7 @@ def create_builtin_groups_and_admin(**kwargs):
     """
     # Check whether there are groups in the database.
     if Group.objects.exists():
-        # Do completely nothing if there are already some of our groups in the database.
+        # Do completely nothing if there are already some groups in the database.
         return
 
     permission_strings = (