diff --git a/jupyter_client/manager.py b/jupyter_client/manager.py
index 07d3ffa3b..343312afb 100644
--- a/jupyter_client/manager.py
+++ b/jupyter_client/manager.py
@@ -11,6 +11,7 @@
 import signal
 import sys
 import time
+import warnings
 
 import zmq