diff --git a/flexeval/core/language_model/vllm_serve_lm.py b/flexeval/core/language_model/vllm_serve_lm.py
index 7bbd09c7..ec469074 100644
--- a/flexeval/core/language_model/vllm_serve_lm.py
+++ b/flexeval/core/language_model/vllm_serve_lm.py
@@ -7,17 +7,19 @@
 import threading
 import time
 from collections.abc import Callable
-from typing import IO, Any
+from typing import IO, TYPE_CHECKING, Any
 
 import requests
 import torch
 from loguru import logger
 
 from flexeval.core.language_model.base import LMOutput
-from flexeval.core.string_processor import StringProcessor
 
 from .openai_api import OpenAIChatAPI
 
+if TYPE_CHECKING:
+    from flexeval.core.string_processor import StringProcessor
+
 
 def find_free_port() -> int:
     with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
@@ -184,6 +186,9 @@ def __init__(
         model_limit_new_tokens: int | None = None,
         tools: list[dict[str, Any]] | None = None,
         max_parallel_requests: int | None = None,
+        max_num_trials: int = 5,
+        first_wait_time: int = 1,
+        max_wait_time: int = 1,
     ) -> None:
         logging.getLogger("httpx").setLevel(logging.WARNING)
         logging.getLogger("httpcore").setLevel(logging.WARNING)
@@ -204,6 +209,9 @@ def __init__(
             model_limit_new_tokens=model_limit_new_tokens,
             tools=tools,
             max_parallel_requests=max_parallel_requests,
+            max_num_trials=max_num_trials,
+            first_wait_time=first_wait_time,
+            max_wait_time=max_wait_time,
         )
 
     @staticmethod