diff --git a/lib/x509.py b/lib/x509.py
index 53b2d6b76..e2021df47 100644
--- a/lib/x509.py
+++ b/lib/x509.py
@@ -17,7 +17,8 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 
-from datetime import datetime, timedelta
+from datetime import datetime
+import sys
 
 try:
     import pyasn1