diff --git a/tests/minitor_test.py b/tests/minitor_test.py
index 4bdb2ce..2a11d20 100644
--- a/tests/minitor_test.py
+++ b/tests/minitor_test.py
@@ -10,5 +10,5 @@ class TestMinitor(object):
         assert ex is None
 
         output, ex = call_output(['ls', '--not-a-real-flag'])
-        assert output.startswith(b'ls: illegal option')
+        assert output.startswith(b'ls: ')
         assert ex is not None