diff --git a/capella2polarion/connectors/polarion_worker.py b/capella2polarion/connectors/polarion_worker.py
index 1c04fe65..ccadad1c 100644
--- a/capella2polarion/connectors/polarion_worker.py
+++ b/capella2polarion/connectors/polarion_worker.py
@@ -175,7 +175,10 @@ def compare_and_update_work_item(
             "Update work item %r for model element %s %r...", *log_args
         )
 
-        old_checksums = {"__C2P__WORK_ITEM": old.get_current_checksum() or ""}
+        if not (old_checksum := old.get_current_checksum() or ""):
+            old_checksum = '{"__C2P__WORK_ITEM": ""}'
+        old_checksums = json.loads(old_checksum)
+
         new_checksum = new.get_current_checksum()
         assert new_checksum is not None
         new_checksums = json.loads(new_checksum)