diff --git a/mjx/mujoco/mjx/_src/collision_driver.py b/mjx/mujoco/mjx/_src/collision_driver.py
index f01c4659..63e8c6e9 100644
--- a/mjx/mujoco/mjx/_src/collision_driver.py
+++ b/mjx/mujoco/mjx/_src/collision_driver.py
@@ -38,7 +38,6 @@ in order to guarantee static shapes for contacts and jacobians.
 """
 
 import itertools
-import os
 from typing import Dict, Iterator, List, Tuple, Union
 
 import jax