diff --git a/run.py b/run.py
index 56a95e294..b04afc11d 100644
--- a/run.py
+++ b/run.py
@@ -10,7 +10,6 @@
 from typing import List, Optional
 
 import numpy as np
-import pyworld as pw
 import soundfile
 import uvicorn
 from fastapi import FastAPI, HTTPException, Request, Response
@@ -129,6 +128,8 @@ def create_accent_phrases(text: str, speaker_id: int) -> List[AccentPhrase]:
     def synthesis_world_params(
         query: AudioQuery, base_speaker: int, target_speaker: int
     ):
+        import pyworld as pw
+
         base_wave = engine.synthesis(query=query, speaker_id=base_speaker).astype(
             "float"
         )
@@ -404,6 +405,8 @@ def synthesis_morphing(
         モーフィングの割合は`morph_rate`で指定でき、0.0でベースの話者、1.0でターゲットの話者に近づきます。
         """
 
+        import pyworld as pw
+
         if morph_rate < 0.0 or morph_rate > 1.0:
             raise HTTPException(
                 status_code=422, detail="morph_rateは0.0から1.0の範囲で指定してください"