diff --git a/openassessment/xblock/ui_mixins/mfe/mixin.py b/openassessment/xblock/ui_mixins/mfe/mixin.py
index 291f1b7cb8..97ed81f52b 100644
--- a/openassessment/xblock/ui_mixins/mfe/mixin.py
+++ b/openassessment/xblock/ui_mixins/mfe/mixin.py
@@ -23,7 +23,7 @@
 from openassessment.xblock.ui_mixins.mfe.constants import error_codes, handler_suffixes
 from openassessment.xblock.ui_mixins.mfe.ora_config_serializer import OraBlockInfoSerializer
 from openassessment.xblock.ui_mixins.mfe.page_context_serializer import PageDataSerializer
-from openassessment.xblock.ui_mixins.mfe.serializers.submission_serializers import UploadFileRequestSerializer
+from openassessment.xblock.ui_mixins.mfe.submission_serializers import AddFileRequestSerializer
 
 
 class OraApiException(JsonHandlerError):
@@ -137,7 +137,7 @@ def _get_new_file_from_list(self, file_to_add, new_list):
         return None
 
     def _file_add(self, data):
-        serializer = UploadFileRequestSerializer(data=data)
+        serializer = AddFileRequestSerializer(data=data)
         if not serializer.is_valid():
             raise OraApiException(400, error_codes.INCORRECT_PARAMETERS, serializer.errors)
         file_to_add = serializer.validated_data
diff --git a/openassessment/xblock/ui_mixins/mfe/submission_serializers.py b/openassessment/xblock/ui_mixins/mfe/submission_serializers.py
index 5cf1def7bc..280e6bfece 100644
--- a/openassessment/xblock/ui_mixins/mfe/submission_serializers.py
+++ b/openassessment/xblock/ui_mixins/mfe/submission_serializers.py
@@ -107,3 +107,13 @@ def get_response(self, data):
         if data['workflow']['has_submitted']:
             return SubmissionSerializer(data['response']).data
         return InProgressResponseSerializer(data).data
+
+
+class AddFileRequestSerializer(Serializer):
+    """
+    Input serializer for file/add handler
+    """
+    fileDescription = CharField(source='description')
+    fileName = CharField(source='name')
+    fileSize = IntegerField(source='size', min_value=0)
+    contentType = CharField()