diff --git a/aliby/tile/traps.py b/aliby/tile/traps.py
index b152261e42544f830150dfe9dd6b1c9b54e4635e..9426377b6ec0519149b52a2524ff7b590981bba8 100644
--- a/aliby/tile/traps.py
+++ b/aliby/tile/traps.py
@@ -2,6 +2,8 @@
 A set of utilities for dealing with ALCATRAS traps
 """
 
+from copy import copy
+
 import numpy as np
 from tqdm import tqdm