diff --git a/src/caosdb/common/models.py b/src/caosdb/common/models.py
index 2217fc9c07d2e90321bf020aae1242248c3f6285..834c6fa558d0220656c4d3bef7845856b4289c66 100644
--- a/src/caosdb/common/models.py
+++ b/src/caosdb/common/models.py
@@ -2819,7 +2819,11 @@ class Container(list):
                     if isinstance(references.value, int):
                         has_references.add(references.value)
                     elif is_list_datatype(references.datatype):
-                        has_references.update(references.value)
+                        for list_item in references.value:
+                            if isinstance(list_item, int): 
+                                has_references.add(list_item)
+                            else:
+                                has_references.add(list_item.id)
                     else:
                         has_references.add(references.value.id)