diff --git a/amodem/calib.py b/amodem/calib.py
index 236f040..8bfca2c 100644
--- a/amodem/calib.py
+++ b/amodem/calib.py
@@ -1,6 +1,5 @@
 import numpy as np
 import logging
-import sys
 
 log = logging.getLogger(__name__)