diff --git a/atroposlib/envs/base.py b/atroposlib/envs/base.py
index 30b32895..b226c24a 100644
--- a/atroposlib/envs/base.py
+++ b/atroposlib/envs/base.py
@@ -1,6 +1,7 @@
 import asyncio
 import json
 import logging
+import string
 import os
 import random
 import sys