diff --git a/tests/unit/cli_test.py b/tests/unit/cli_test.py
index 9700d59272..2c90b29b72 100644
--- a/tests/unit/cli_test.py
+++ b/tests/unit/cli_test.py
@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 import os
 import shutil
 import tempfile
-from StringIO import StringIO
+from io import StringIO
 
 import docker
 import py