diff --git a/src/collective/exportimport/serializer.py b/src/collective/exportimport/serializer.py
index eff23154..2530d426 100644
--- a/src/collective/exportimport/serializer.py
+++ b/src/collective/exportimport/serializer.py
@@ -90,10 +90,12 @@ def __call__(self):
             return None
 
         try:
-            if "built-in function id" in namedfile.filename:
+            if namedfile.filename and "built-in function id" in namedfile.filename:
                 filename = self.context.id
             else:
                 filename = namedfile.filename
+            if not filename:
+                filename = self.context.id
         except AttributeError:
             # Try to recover broken namedfile
             # Related to: WARNING OFS.Uninstalled Could not import class 'NamedBlobFile' from module 'zope.app.file.file'