diff --git a/openslides/mediafiles/serializers.py b/openslides/mediafiles/serializers.py
index 4f4b0e360..b86f6b2f4 100644
--- a/openslides/mediafiles/serializers.py
+++ b/openslides/mediafiles/serializers.py
@@ -37,6 +37,8 @@ class MediafileSerializer(ModelSerializer):
         """
         super(MediafileSerializer, self).__init__(*args, **kwargs)
         self.serializer_field_mapping[dbmodels.FileField] = AngularCompatibleFileField
+        if self.instance is not None:
+            self.fields['mediafile'].read_only = True
 
     class Meta:
         model = Mediafile
diff --git a/openslides/mediafiles/views.py b/openslides/mediafiles/views.py
index 08b300422..6c09f0b61 100644
--- a/openslides/mediafiles/views.py
+++ b/openslides/mediafiles/views.py
@@ -1,4 +1,4 @@
-from ..utils.rest_api import ModelViewSet
+from ..utils.rest_api import ModelViewSet, ValidationError
 from .models import Mediafile
 from .serializers import MediafileSerializer
 
@@ -45,4 +45,6 @@ class MediafileViewSet(ModelViewSet):
                 not request.user.has_perm('mediafiles.can_manage') and
                 str(self.request.user.pk) != str(uploader_id)):
             self.permission_denied(request)
+        if not self.request.data.get('mediafile'):
+            raise ValidationError({'details': 'You forgot to provide a file.'})
         return super().create(request, *args, **kwargs)