diff --git a/artiq/gateware/targets/kc705.py b/artiq/gateware/targets/kc705.py
index c74a72cdc..b4dae91ae 100755
--- a/artiq/gateware/targets/kc705.py
+++ b/artiq/gateware/targets/kc705.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python3.5
 
 import argparse
+import sys
 
 from migen import *
 from migen.genlib.resetsync import AsyncResetSynchronizer