diff --git a/tests/unit/channel_test.py b/tests/unit/channel_test.py
index 8bb6d1d54..c2b02d651 100644
--- a/tests/unit/channel_test.py
+++ b/tests/unit/channel_test.py
@@ -101,7 +101,7 @@ def test_send_signal(ssh_channel):
     ssh_channel.request_exec('bash -c \'trap "exit 1" SIGUSR1; echo ready; sleep 5; exit 0\'')
 
     # Wait until the process is ready to receive signal
-    data = ""
+    data = ''
     while not data.startswith('ready'):
         ssh_channel.poll(timeout=1000)
         data += ssh_channel.recv().decode('utf-8')