diff --git a/lib/galaxy/model/__init__.py b/lib/galaxy/model/__init__.py
index 335a8e462f68..b82591ca49b5 100644
--- a/lib/galaxy/model/__init__.py
+++ b/lib/galaxy/model/__init__.py
@@ -3733,8 +3733,8 @@ def _serialize(self, id_encoder, serialization_options):
         # serialize Dataset objects only for jobs that can actually modify these models.
         assert serialization_options.serialize_dataset_objects
 
-        def to_int(n):
-            return int(n) if n is not None else 0
+        def to_int(n) -> Optional[int]:
+            return int(n) if n is not None else None
 
         rval = dict_for(
             self,
diff --git a/lib/galaxy/model/store/__init__.py b/lib/galaxy/model/store/__init__.py
index 122af7529555..cee81a526cbb 100644
--- a/lib/galaxy/model/store/__init__.py
+++ b/lib/galaxy/model/store/__init__.py
@@ -650,6 +650,8 @@ def handle_dataset_object_edit(dataset_instance, dataset_attrs):
                                         file_name=source,
                                         create=True,
                                     )
+                        # Don't trust serialized file size
+                        dataset_instance.dataset.file_size = None
                         dataset_instance.dataset.set_total_size()  # update the filesize record in the database
 
                     if dataset_instance.deleted: