diff --git a/nenupy/schedule/contamination.py b/nenupy/schedule/contamination.py
index 299304f..24d1ed7 100644
--- a/nenupy/schedule/contamination.py
+++ b/nenupy/schedule/contamination.py
@@ -22,7 +22,7 @@
 
 
 import logging
-from threading import local
+
 log = logging.getLogger(__name__)
 
 import numpy as np