diff --git a/numba/tests/test_help.py b/numba/tests/test_help.py
index a78f05f0a3c..8199d4c93c4 100644
--- a/numba/tests/test_help.py
+++ b/numba/tests/test_help.py
@@ -89,4 +89,4 @@ def test_inspect_cli(self):
         with self.assertRaises(subprocess.CalledProcessError) as raises:
             subprocess.check_output(cmds, stderr=subprocess.STDOUT)
         self.assertIn("\'foo\' is not supported",
-                      raises.exception.stdout.decode('ascii'))
+                      raises.exception.stdout.decode())