diff --git a/optuna_dashboard/app.py b/optuna_dashboard/app.py
index 18ecfe38..826fcd88 100644
--- a/optuna_dashboard/app.py
+++ b/optuna_dashboard/app.py
@@ -8,7 +8,8 @@ from ._app import create_app as _create_app
 
 def create_app(storage: BaseStorage) -> Bottle:
     warnings.warn(
-        "This function will be removed in the future. Please use optuna_dashboard.run_server() instead.",
+        "This function will be removed in the future."
+        " Please use optuna_dashboard.run_server() instead.",
         DeprecationWarning,
     )
     return _create_app(storage)