diff --git a/ocrd_models/ocrd_page_user_methods/id.py b/ocrd_models/ocrd_page_user_methods/id.py
index <HASH>..<HASH> 100644
--- a/ocrd_models/ocrd_page_user_methods/id.py
+++ b/ocrd_models/ocrd_page_user_methods/id.py
@@ -1,5 +1,5 @@
 @property
 def id(self):
     if hasattr(self, 'pcGtsId'):
-        return self.pcGtsId
+        return self.pcGtsId or ''
     return self.imageFilename
handle unset pcGtsId