diff --git a/openslides/agenda/slides.py b/openslides/agenda/slides.py
index a0da4f60c..ce0c3219a 100644
--- a/openslides/agenda/slides.py
+++ b/openslides/agenda/slides.py
@@ -3,7 +3,8 @@
 from django.template.loader import render_to_string
 
 from openslides.config.api import config
-from openslides.projector.api import get_projector_content, register_slide
+from openslides.projector.api import (
+    get_projector_content, register_slide, SlideError)
 
 from .models import Item
 
@@ -28,7 +29,7 @@ def agenda_slide(**kwargs):
     try:
         item = Item.objects.get(pk=item_pk)
     except Item.DoesNotExist:
-        item = None
+        raise SlideError
 
     if slide_type == 'summary' or item is None:
         context = {}
@@ -38,7 +39,7 @@ def agenda_slide(**kwargs):
             items = item.get_children().filter(type__exact=Item.AGENDA_ITEM)
             context['title'] = item.get_title()
         context['items'] = items
-        return render_to_string('agenda/item_slide_summary.html', context)
+        slide = render_to_string('agenda/item_slide_summary.html', context)
 
     elif slide_type == 'list_of_speakers':
         list_of_speakers = item.get_list_of_speakers(
@@ -46,17 +47,18 @@ def agenda_slide(**kwargs):
         context = {'title': item.get_title(),
                    'item': item,
                    'list_of_speakers': list_of_speakers}
-        return render_to_string('agenda/item_slide_list_of_speaker.html', context)
+        slide = render_to_string('agenda/item_slide_list_of_speaker.html', context)
 
     elif item.content_object:
         slide_dict = {
             'callback': item.content_object.slide_callback_name,
             'pk': item.content_object.pk}
-        return get_projector_content(slide_dict)
+        slide = get_projector_content(slide_dict)
 
     else:
         context = {'item': item}
-        return render_to_string('agenda/item_slide.html', context)
+        slide = render_to_string('agenda/item_slide.html', context)
+    return slide
 
 
 register_slide('agenda', agenda_slide)
diff --git a/openslides/mediafile/slides.py b/openslides/mediafile/slides.py
index 61ce6c1c9..ba8f7ff51 100644
--- a/openslides/mediafile/slides.py
+++ b/openslides/mediafile/slides.py
@@ -4,7 +4,7 @@
 from django.template.loader import render_to_string
 
 from openslides.config.api import config
-from openslides.projector.api import register_slide
+from openslides.projector.api import register_slide, SlideError
 
 from .models import Mediafile
 
@@ -24,8 +24,7 @@ def mediafile_presentation_as_slide(**kwargs):
             filetype__in=Mediafile.PRESENTABLE_FILE_TYPES,
             is_presentable=True)
     except Mediafile.DoesNotExist:
-        # TODO what doing, if a wrong pk is given?
-        pdf = None
+        raise SlideError
     context = {'pdf': pdf, 'page_num': page_num,
                'fullscreen': config['pdf_fullscreen']}
     return render_to_string('mediafile/presentation_slide.html', context)
diff --git a/openslides/projector/api.py b/openslides/projector/api.py
index 2ab8ea176..f091815cc 100644
--- a/openslides/projector/api.py
+++ b/openslides/projector/api.py
@@ -10,6 +10,7 @@ from django.utils.importlib import import_module
 
 from openslides.config.api import config
 from openslides.utils.tornado_webserver import ProjectorSocketHandler
+from openslides.utils.exceptions import OpenSlidesError
 
 from .signals import projector_overlays
 
@@ -20,6 +21,10 @@ callable object which returns the html code for a slide.
 """
 
 
+class SlideError(OpenSlidesError):
+    pass
+
+
 def update_projector():
     """
     Sends the data to the clients, who listen to the projector.
@@ -82,7 +87,7 @@ def get_projector_content(slide_dict=None):
 
     try:
         slide_content = slide_callback[callback](**slide_dict)
-    except KeyError:
+    except (KeyError, SlideError):
         slide_content = default_slide()
     return slide_content
 
@@ -158,8 +163,7 @@ def register_slide_model(SlideModel, template):
         try:
             slide = SlideModel.objects.get(pk=slide_pk)
         except SlideModel.DoesNotExist:
-            slide = None
-            context = {'slide': None}
+            raise SlideError
         else:
             context = slide.get_slide_context()
 
diff --git a/tests/projector/test_api.py b/tests/projector/test_api.py
index 75bc04236..253ee9501 100644
--- a/tests/projector/test_api.py
+++ b/tests/projector/test_api.py
@@ -77,6 +77,10 @@ class ApiFunctions(TestCase):
                 value = projector_api.get_projector_content()
                 self.assertEqual(value, 'slide content')
 
+            mock_slide.side_effect = projector_api.SlideError
+            projector_api.get_projector_content({'callback': 'mock_slide'})
+            self.assertTrue(mock_default_slide.called)
+
     @patch('openslides.projector.api.render_to_string')
     def test_default_slide(self, mock_render_to_string):
         projector_api.default_slide()
@@ -159,8 +163,7 @@ class ApiFunctions(TestCase):
 
         # Test with non existing object
         mock_SlideModel.objects.get.side_effect = Exception
-        used_args[1](pk=1)
-        mock_render_to_string.assert_called_with('some template', {'slide': None})
+        self.assertRaises(projector_api.SlideError, used_args[1], pk=1)
 
     @patch('openslides.projector.api.update_projector_overlay')
     @patch('openslides.projector.api.update_projector')