diff --git a/lib/transaction.py b/lib/transaction.py
index 57339849c..6d1eee1d0 100644
--- a/lib/transaction.py
+++ b/lib/transaction.py
@@ -24,6 +24,7 @@ import bitcoin
 from bitcoin import *
 from util import print_error
 import time
+import sys
 import struct
 
 #