diff --git a/src/linkahead/common/models.py b/src/linkahead/common/models.py
index 2828b1ad5bbe84e1120d0da65f23686d9245212a..c7a9cd6d5ca5eccfcbdee009548b18eaa65b1215 100644
--- a/src/linkahead/common/models.py
+++ b/src/linkahead/common/models.py
@@ -3445,7 +3445,7 @@ class Container(list):
 
             for prop in container_item.get_properties():
                 prop_dt = prop.datatype
-                if is_reference(prop_dt):
+                if prop_dt is not None and is_reference(prop_dt):
                     # add only if it is a reference, not a simple property
                     # Step 1: look for prop.value
                     if prop.value is not None: