diff --git a/api/db/services/llm_service.py b/api/db/services/llm_service.py
index 258a4bf92..d669cdd90 100644
--- a/api/db/services/llm_service.py
+++ b/api/db/services/llm_service.py
@@ -16,6 +16,7 @@
 import logging
 import re
 from functools import partial
+from typing import Generator
 
 from langfuse import Langfuse
 
@@ -57,7 +58,6 @@ class TenantLLMService(CommonService):
                 mdlnm += "___OpenAI-API"
             elif fid == "VLLM":
                 mdlnm += "___VLLM"
-                
             objs = cls.query(tenant_id=tenant_id, llm_name=mdlnm, llm_factory=fid)
         if not objs:
             return
@@ -334,7 +334,7 @@ class LLMBundle:
 
         return txt
 
-    def tts(self, text: str) -> None:
+    def tts(self, text: str) -> Generator[bytes, None, None]:
         if self.langfuse:
             span = self.trace.span(name="tts", input={"text": text})