diff --git a/artiq/devices/ctlmgr.py b/artiq/devices/ctlmgr.py
index 785f67267..c4873a66e 100644
--- a/artiq/devices/ctlmgr.py
+++ b/artiq/devices/ctlmgr.py
@@ -3,6 +3,7 @@ import logging
 import subprocess
 import shlex
 import socket
+import os
 
 from artiq.protocols.sync_struct import Subscriber
 from artiq.protocols.pc_rpc import AsyncioClient