diff --git a/rag/app/picture.py b/rag/app/picture.py
index d8332fd76..2ad773a3c 100644
--- a/rag/app/picture.py
+++ b/rag/app/picture.py
@@ -78,10 +78,10 @@ def chunk(filename, binary, tenant_id, lang, callback=None, **kwargs):
         try:
             callback(0.4, "Use CV LLM to describe the picture.")
             cv_mdl = LLMBundle(tenant_id, LLMType.IMAGE2TEXT, lang=lang)
-            img_binary = io.BytesIO()
-            img.save(img_binary, format="JPEG")
-            img_binary.seek(0)
-            ans = cv_mdl.describe(img_binary.read())
+            with io.BytesIO() as img_binary:
+                img.save(img_binary, format="JPEG")
+                img_binary.seek(0)
+                ans = cv_mdl.describe(img_binary.read())
             callback(0.8, "CV LLM respond: %s ..." % ans[:32])
             txt += "\n" + ans
             tokenize(doc, txt, eng)