diff --git a/rag/raptor.py b/rag/raptor.py
index 20ad8638b..2d3ccfa7d 100644
--- a/rag/raptor.py
+++ b/rag/raptor.py
@@ -63,7 +63,7 @@ class RecursiveAbstractiveProcessing4TreeOrganizedRetrieval:
         last_exc = None
         for attempt in range(3):
             try:
-                response = await asyncio.to_thread(self._llm_model.chat, system, history, gen_conf)
+                response = await self._llm_model.async_chat(system, history, gen_conf)
                 response = re.sub(r"^.*</think>", "", response, flags=re.DOTALL)
                 if response.find("**ERROR**") >= 0:
                     raise Exception(response)