diff --git a/app/src/db/bulk_ops.py b/app/src/db/bulk_ops.py
index 8c6c6e7..1d7bd2a 100644
--- a/app/src/db/bulk_ops.py
+++ b/app/src/db/bulk_ops.py
@@ -2,7 +2,7 @@
 
 Provides a bulk_upsert function
 """
-from typing import Any, Sequence
+from typing import Any, Optional, Sequence
 
 import psycopg
 from psycopg import rows, sql
@@ -11,8 +11,6 @@
 Cursor = psycopg.Cursor
 kwargs_row = rows.kwargs_row
 
-EMPTY_SQL = sql.SQL("")
-
 
 def bulk_upsert(
     cur: psycopg.Cursor,
@@ -20,7 +18,7 @@ def bulk_upsert(
     attributes: Sequence[str],
     objects: Sequence[Any],
     constraint: str,
-    update_condition: sql.SQL = EMPTY_SQL,
+    update_condition: Optional[sql.SQL] = None,
 ) -> None:
     """Bulk insert or update a sequence of objects.
 
@@ -37,6 +35,9 @@ def bulk_upsert(
       update_condition: optional WHERE clause to limit updates for a
         conflicting row
     """
+    if not update_condition:
+        update_condition = sql.SQL("")
+
     temp_table = f"temp_{table}"
     create_temp_table(cur, temp_table=temp_table, src_table=table)
     bulk_insert(cur, table=temp_table, columns=attributes, objects=objects)
@@ -103,7 +104,7 @@ def write_from_table_to_table(
     dest_table: str,
     columns: Sequence[str],
     constraint: str,
-    update_condition: sql.SQL = EMPTY_SQL,
+    update_condition: Optional[sql.SQL] = None,
 ) -> None:
     """
     Write data from one table to another.
@@ -117,6 +118,9 @@ def write_from_table_to_table(
       update_condition: optional WHERE clause to limit updates for a
         conflicting row
     """
+    if not update_condition:
+        update_condition = sql.SQL("")
+
     columns_sql = sql.SQL(",").join(map(sql.Identifier, columns))
     update_sql = sql.SQL(",").join(
         [