diff --git a/bin/zol b/bin/zol
index 6d29e62..63ab9cd 100644
--- a/bin/zol
+++ b/bin/zol
@@ -45,6 +45,7 @@ import shutil
 import subprocess
 import pickle
 from datetime import datetime
+from collections import defaultdict
 import traceback
 
 def create_parser():