diff --git a/.travis.yml b/.travis.yml
index a051acc92..142b08c05 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,7 +18,7 @@ script:
   - "isort --check-only --recursive openslides tests"
 
   - "DJANGO_SETTINGS_MODULE='tests.settings' coverage run ./manage.py test tests.unit"
-  - "coverage report --fail-under=42"
+  - "coverage report --fail-under=43"
 
   - "DJANGO_SETTINGS_MODULE='tests.settings' coverage run ./manage.py test tests.integration"
   - "coverage report --fail-under=50"
diff --git a/openslides/agenda/projector.py b/openslides/agenda/projector.py
index 13dac488c..c55356737 100644
--- a/openslides/agenda/projector.py
+++ b/openslides/agenda/projector.py
@@ -23,15 +23,10 @@ class ItemListSlide(ProjectorElement):
 
     def get_context(self):
         pk = self.config_entry.get('id')
-        if pk is None:
-            # Root list slide.
-            context = {'tree':  self.config_entry.get('tree', False)}
-        else:
+        if pk is not None:
             # Children slide.
             if not Item.objects.filter(pk=pk).exists():
                 raise ProjectorException(_('Item does not exist.'))
-            context = {'id': pk, 'tree':  self.config_entry.get('tree', False)}
-        return context
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id', 'tree')
@@ -65,7 +60,6 @@ class ItemDetailSlide(ProjectorElement):
             raise ProjectorException(_('Id must not be None.'))
         if not Item.objects.filter(pk=pk).exists():
             raise ProjectorException(_('Item does not exist.'))
-        return {'id': pk, 'list_of_speakers': self.config_entry.get('list_of_speakers', False)}
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id')
diff --git a/openslides/agenda/static/js/agenda/agenda.js b/openslides/agenda/static/js/agenda/agenda.js
index e9b33b1bb..36b40a59f 100644
--- a/openslides/agenda/static/js/agenda/agenda.js
+++ b/openslides/agenda/static/js/agenda/agenda.js
@@ -392,12 +392,12 @@ angular.module('OpenSlidesApp.agenda.projector', ['OpenSlidesApp.agenda'])
         // Attention! Each object that is used here has to be dealt on server side.
         // Add it to the coresponding get_requirements method of the ProjectorElement
         // class.
-        var id = $scope.element.context.id;
+        var id = $scope.element.id;
         Agenda.find(id);
         User.findAll();
         Agenda.bindOne(id, $scope, 'item');
         // get flag for list-of-speakers-slide (true/false)
-        $scope.is_list_of_speakers = $scope.element.context.list_of_speakers;
+        $scope.is_list_of_speakers = $scope.element.list_of_speakers;
     }
 ])
 
diff --git a/openslides/assignments/projector.py b/openslides/assignments/projector.py
index 6687ed11d..205c559c3 100644
--- a/openslides/assignments/projector.py
+++ b/openslides/assignments/projector.py
@@ -18,15 +18,10 @@ class AssignmentSlide(ProjectorElement):
 
     def get_context(self):
         pk = self.config_entry.get('id')
-        if pk is None:
-            # List slide.
-            context = None
-        else:
+        if pk is not None:
             # Detail slide.
             if not Assignment.objects.filter(pk=pk).exists():
                 raise ProjectorException(_('Assignment does not exist.'))
-            context = {'id': pk}
-        return context
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id')
diff --git a/openslides/assignments/static/js/assignments/assignments.js b/openslides/assignments/static/js/assignments/assignments.js
index c9f4ced1d..cd179a984 100644
--- a/openslides/assignments/static/js/assignments/assignments.js
+++ b/openslides/assignments/static/js/assignments/assignments.js
@@ -131,7 +131,7 @@ angular.module('OpenSlidesApp.assignments.projector', ['OpenSlidesApp.assignment
     // Attention! Each object that is used here has to be dealt on server side.
     // Add it to the coresponding get_requirements method of the ProjectorElement
     // class.
-    var id = $scope.element.context.id;
+    var id = $scope.element.id;
     Assignment.find(id);
     Assignment.bindOne(id, $scope, 'assignment');
 });
diff --git a/openslides/core/models.py b/openslides/core/models.py
index 09bbade37..bc3864d63 100644
--- a/openslides/core/models.py
+++ b/openslides/core/models.py
@@ -68,7 +68,8 @@ class Projector(RESTModelMixin, models.Model):
         # Parse result
         result = {}
         for key, value in self.config.items():
-            result[key] = value
+            # Use a copy here not to change the origin value in the config field.
+            result[key] = value.copy()
             element = elements.get(value['name'])
             if element is None:
                 result[key]['error'] = _('Projector element does not exist.')
diff --git a/openslides/core/projector.py b/openslides/core/projector.py
index 58ebe4088..ef1d7b1a0 100644
--- a/openslides/core/projector.py
+++ b/openslides/core/projector.py
@@ -16,10 +16,8 @@ class CustomSlideSlide(ProjectorElement):
     name = 'core/customslide'
 
     def get_context(self):
-        pk = self.config_entry.get('id')
-        if not CustomSlide.objects.filter(pk=pk).exists():
+        if not CustomSlide.objects.filter(pk=self.config_entry.get('id')).exists():
             raise ProjectorException(_('Custom slide does not exist.'))
-        return {'id': pk}
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id')
diff --git a/openslides/core/serializers.py b/openslides/core/serializers.py
index 7fb6db583..d541d6cbe 100644
--- a/openslides/core/serializers.py
+++ b/openslides/core/serializers.py
@@ -9,30 +9,28 @@ class JSONSerializerField(Field):
     """
     def to_internal_value(self, data):
         """
-        Checks that data is a list of dictionaries. Every dictionary must have
-        a key 'name'.
+        Checks that data is a dictionary. The key is a hex UUID and the
+        value is a dictionary with must have a key 'name'.
         """
-        if type(data) is not list:
-            raise ValidationError('Data must be a list of dictionaries.')
-        for element in data:
+        if type(data) is not dict:
+            raise ValidationError('Data must be a dictionary.')
+        for element in data.values():
             if type(element) is not dict:
-                raise ValidationError('Data must be a list of dictionaries.')
+                raise ValidationError('Data must be a dictionary.')
             elif element.get('name') is None:
                 raise ValidationError("Every dictionary must have a key 'name'.")
         return data
 
-    def to_representation(self, value):
-        return value
-
 
 class ProjectorSerializer(ModelSerializer):
     """
     Serializer for core.models.Projector objects.
     """
+    config = JSONSerializerField(write_only=True)
 
     class Meta:
         model = Projector
-        fields = ('id', 'elements', )
+        fields = ('id', 'config', 'elements', )
 
 
 class CustomSlideSerializer(ModelSerializer):
diff --git a/openslides/core/static/js/core/core.js b/openslides/core/static/js/core/core.js
index df7f58d7a..d9d08010c 100644
--- a/openslides/core/static/js/core/core.js
+++ b/openslides/core/static/js/core/core.js
@@ -765,7 +765,7 @@ angular.module('OpenSlidesApp.core.projector', ['OpenSlidesApp.core'])
     // Attention! Each object that is used here has to be dealt on server side.
     // Add it to the coresponding get_requirements method of the ProjectorElement
     // class.
-    var id = $scope.element.context.id;
+    var id = $scope.element.id;
     Customslide.find(id);
     Customslide.bindOne(id, $scope, 'customslide');
 })
diff --git a/openslides/motions/projector.py b/openslides/motions/projector.py
index 656ecea61..04b5a12a7 100644
--- a/openslides/motions/projector.py
+++ b/openslides/motions/projector.py
@@ -18,15 +18,10 @@ class MotionSlide(ProjectorElement):
 
     def get_context(self):
         pk = self.config_entry.get('id')
-        if pk is None:
-            # List slide.
-            context = None
-        else:
+        if pk is not None:
             # Detail slide.
             if not Motion.objects.filter(pk=pk).exists():
                 raise ProjectorException(_('Motion does not exist.'))
-            context = {'id': pk}
-        return context
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id')
diff --git a/openslides/motions/static/js/motions/motions.js b/openslides/motions/static/js/motions/motions.js
index e6fc8711d..a9c612596 100644
--- a/openslides/motions/static/js/motions/motions.js
+++ b/openslides/motions/static/js/motions/motions.js
@@ -348,7 +348,7 @@ angular.module('OpenSlidesApp.motions.projector', ['OpenSlidesApp.motions'])
     // Attention! Each object that is used here has to be dealt on server side.
     // Add it to the coresponding get_requirements method of the ProjectorElement
     // class.
-    var id = $scope.element.context.id;
+    var id = $scope.element.id;
     Motion.find(id);
     Motion.bindOne(id, $scope, 'motion');
 });
diff --git a/openslides/users/projector.py b/openslides/users/projector.py
index 5360dd469..2ec339477 100644
--- a/openslides/users/projector.py
+++ b/openslides/users/projector.py
@@ -14,10 +14,8 @@ class UserSlide(ProjectorElement):
     name = 'users/user'
 
     def get_context(self):
-        pk = self.config_entry.get('id')
-        if not User.objects.filter(pk=pk).exists():
+        if not User.objects.filter(pk=self.config_entry.get('id')).exists():
             raise ProjectorException(_('User does not exist.'))
-        return {'id': pk}
 
     def get_requirements(self, config_entry):
         pk = config_entry.get('id')
diff --git a/openslides/users/static/js/users/users.js b/openslides/users/static/js/users/users.js
index 32bfbe85a..af2aa45e6 100644
--- a/openslides/users/static/js/users/users.js
+++ b/openslides/users/static/js/users/users.js
@@ -547,7 +547,7 @@ angular.module('OpenSlidesApp.users.projector', ['OpenSlidesApp.users'])
     // Attention! Each object that is used here has to be dealt on server side.
     // Add it to the coresponding get_requirements method of the ProjectorElement
     // class.
-    var id = $scope.element.context.id;
+    var id = $scope.element.id;
     User.find(id);
     User.bindOne(id, $scope, 'user');
 });
diff --git a/tests/integration/core/test_views.py b/tests/integration/core/test_views.py
index 4cb5d08f0..bd95f2b50 100644
--- a/tests/integration/core/test_views.py
+++ b/tests/integration/core/test_views.py
@@ -34,7 +34,7 @@ class ProjectorAPI(TestCase):
                 'aae4a07b26534cfb9af4232f361dce73':
                     {'id': customslide.id,
                      'name': 'core/customslide',
-                     'context': {'id': customslide.id}}}})
+                     'context': None}}})
 
     def test_invalid_slide_on_default_projector(self):
         self.client.login(username='admin', password='admin')
diff --git a/tests/unit/core/test_views.py b/tests/unit/core/test_views.py
index bb17cd082..7012b4d91 100644
--- a/tests/unit/core/test_views.py
+++ b/tests/unit/core/test_views.py
@@ -86,8 +86,7 @@ class ProjectorAPI(TestCase):
             'test_key_mud1shoo8moh6eiXoong': 'test_value_shugieJier6agh1Ehie3'}]
         self.viewset.request = request
         self.viewset.prune_elements(request=request, pk=MagicMock())
-        # TODO: Do not know how to test this.
-        # self.assertEqual(len(mock_object.return_value.config), 2)
+        self.assertEqual(len(mock_object.return_value.config), 2)
 
     def test_update_elements(self, mock_object):
         mock_object.return_value.config = {
@@ -170,8 +169,7 @@ class ProjectorAPI(TestCase):
         request = MagicMock()
         self.viewset.request = request
         self.viewset.clear_elements(request=request, pk=MagicMock())
-        # TODO: Do not know how to test this.
-        # self.assertEqual(len(mock_object.return_value.config), 0)
+        self.assertEqual(len(mock_object.return_value.config), 0)
 
     def test_clear_elements_with_stable(self, mock_object):
         mock_object.return_value.config = {