diff --git a/lib/galaxy/managers/hdas.py b/lib/galaxy/managers/hdas.py
index 17abe5063337..09354dd71ebc 100644
--- a/lib/galaxy/managers/hdas.py
+++ b/lib/galaxy/managers/hdas.py
@@ -21,6 +21,8 @@
     desc,
     false,
     func,
+    nulls_first,
+    nulls_last,
     select,
     true,
 )
@@ -347,8 +349,8 @@ def __init__(self, hda_manager: HDAManager, dataset_manager: datasets.DatasetMan
         self.sort_map = {
             StoredItemOrderBy.NAME_ASC: asc(model.HistoryDatasetAssociation.name),
             StoredItemOrderBy.NAME_DSC: desc(model.HistoryDatasetAssociation.name),
-            StoredItemOrderBy.SIZE_ASC: asc(model.Dataset.total_size),
-            StoredItemOrderBy.SIZE_DSC: desc(model.Dataset.total_size),
+            StoredItemOrderBy.SIZE_ASC: nulls_first(asc(model.Dataset.total_size)),
+            StoredItemOrderBy.SIZE_DSC: nulls_last(desc(model.Dataset.total_size)),
             StoredItemOrderBy.UPDATE_TIME_ASC: asc(model.HistoryDatasetAssociation.update_time),
             StoredItemOrderBy.UPDATE_TIME_DSC: desc(model.HistoryDatasetAssociation.update_time),
         }