diff --git a/rag/nlp/synonym.py b/rag/nlp/synonym.py
index 0956ee8e83..53a4ce1f1c 100644
--- a/rag/nlp/synonym.py
+++ b/rag/nlp/synonym.py
@@ -23,6 +23,13 @@ from nltk.corpus import wordnet
 from common.file_utils import get_project_base_directory
 
 
+# Forces NLTK to load the corpus synchronously once, preventing concurrent tasks
+# from triggering the lazy-loading race condition.
+try:
+    wordnet.ensure_loaded()
+except Exception:
+    logging.warning("Fail to load wordnet.ensure_loaded()")
+
 class Dealer:
     def __init__(self, redis=None):