diff --git a/scripts/marker_reprocess_existing_success.py b/scripts/marker_reprocess_existing_success.py
index 04e56c0..48f58a4 100644
--- a/scripts/marker_reprocess_existing_success.py
+++ b/scripts/marker_reprocess_existing_success.py
@@ -126,9 +126,11 @@ async def run(*, apply: bool, only_ids: set[int] | None, snapshot_csv: str | Non
 
             # enqueue — UNIQUE(document_id, stage) WHERE status IN ('pending', 'processing')
             # 가 있으므로 활성 markdown 행이 없는 doc 만 통과. 충돌 시 silent skip.
+            # CAST(:payload AS jsonb) — `::jsonb` postfix 캐스트는 SQLAlchemy text()
+            # 의 named-param prefix `:` 와 충돌해 syntax error 발생.
             ENQUEUE_SQL = text("""
                 INSERT INTO processing_queue (document_id, stage, status, payload)
-                VALUES (:doc_id, 'markdown', 'pending', :payload::jsonb)
+                VALUES (:doc_id, 'markdown', 'pending', CAST(:payload AS jsonb))
                 ON CONFLICT DO NOTHING
             """)