diff --git a/opentech/apply/stream_forms/blocks.py b/opentech/apply/stream_forms/blocks.py
index d911275742eb4d0f1f8444bce96aa649a2d2563f..67730468d785ec6b7f043d4459caca42bafb6f5c 100644
--- a/opentech/apply/stream_forms/blocks.py
+++ b/opentech/apply/stream_forms/blocks.py
@@ -298,7 +298,9 @@ class UploadableMediaBlock(OptionalFormFieldBlock):
 
     def prepare_data(self, value, data, serialize):
         if serialize:
-            return data.serialize()
+            if data:
+                return data.serialize()
+            return None
 
         return data