diff --git a/elastica/rod/knot_theory.py b/elastica/rod/knot_theory.py
index 1b7a834db..23d2b009f 100644
--- a/elastica/rod/knot_theory.py
+++ b/elastica/rod/knot_theory.py
@@ -10,8 +10,6 @@
 The details discussion is included in `N Charles et. al. PRL (2019) <https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.208003>`_.
 """
 
-import sys
-
 from typing import Protocol, Union
 
 from numba import njit